The Provider Primer Series: Diagnosis and natural history of systemic mastocytosis (ISM, SSM, ASM)

Systemic mastocytosis (SM) is a primary hematologic disorder marked by the excessive proliferation of mast cells.

Neoplastic nature of mastocytosis:

  • Mast cells produced in this disease are neoplastic and may have some or all of the following markers: presence of somatic gain-of-function mutation at codon 816 of CKIT (KIT), usually, but not always, the D816V mutation; expression of CD2 or CD25 on mast cell surface; atypical spindled morphology of mast cells[i].
  • Mastocytosis is a neoplastic condition that is not described exclusively by excessive population of mast cells. Mast cell hyperplasia can occur in response to a number of conditions including chronic urticaria[ii], irritable bowel syndrome[iii], and other hematologic neoplasia, including chronic lymphocytic leukemia, non-Hodgkin lymphoma, and myeloproliferative conditions[iv].
  • To meet criteria for SM, mast cell infiltration must be dense with at least 15 mast cells per cluster. In many instances, there is not a validated range of mast cells/hpf in healthy controls[iv].
Table 1: Diagnostic criteria for systemic mastocytosis[v]

1 major and 1 minor criterion; or 3 minor criteria

Major Multifocal dense infiltrates of mast cells (15 or more in aggregate) detected in sections of bone marrow and/or extracutaneous organ
Minor In biopsy sections, more than 25% of mast cells in infiltrated space are spindle-shaped or otherwise morphologically abnormal; or, of all mast cells in bone marrow aspirate smears, more than 25% mast cells are immature or abnormal. Detection of CKIT mutation at codon 816 in bone marrow, blood or extracutaneous organ Mast cells in bone marrow, blood or other extracutaneous organ that co-expresses CD-117 with CD2 and/or CD25 Baseline serum tryptase of 20 ng/ml or higher.

 

Presence of dense infiltrates:

  • The hallmark sign of systemic mastocytosis is multifocal dense infiltration of an organ that is not the skin. Despite this fact, it is possible to biopsy negative while still having SM. A 2004 study reported the pathological findings of bilateral bone marrow biopsies for 23 patients. 83% of patients demonstrated positive biopsy for SM bilaterally while 17% of patients had only one positive biopsy[vi].
  • One study found that 20% of ISM patients did not have dense infiltration of mast cells in bone marrow[vii].

Tryptase level in systemic mastocytosis:

  • Tryptase ≥20 ng/mL is a minor criterion for SM. In order to meet this criterion, tryptase must be ≥20 ng/mL at baseline, not during or following a reactive or anaphylactic event. Per Phadia, producer of ImmunoCAP® Tryptase test, it can take up to fourteen days for tryptase to return to baseline[viii]. However, other sources recommend shorter time to baseline, as low as “24 hours after clinical signs and symptoms have completely subsided”[ix].
  • 20-30% of SM patients do not meet the minor criterion of tryptase level ≥20 ng/mL[xiii].

Detection of CKIT D816V mutation:

  • The CKIT D816V mutation may not be detected in peripheral blood in a positive patient. Bone marrow aspirate is the preferred sample type for reliable testing for this mutation[xii].
  • One study reported as few as 78% of ISM patients were positive for the CKIT D816V mutation in bone marrow[xiii].

Natural history of indolent systemic mastocytosis:

  • Indolent systemic mastocytosis (ISM) is SM that does not meet criteria for smoldering systemic mastocytosis, aggressive systemic mastocytosis or mast cell leukemia.
  • ISM is largely described by mediator release symptoms and increased risk of anaphylaxis. Mast cell infiltration does not cause appreciable organ dysfunction in this variant[x].
  • Progression from ISM to SSM occurred in about 8% of patients in a cohort of 74. In this same cohort, 4% ISM patients progressed to ASM[xi]. The risk of leukemic transformation from ISM was 0.6% in a cohort of 159[xii].
  • Organomegaly can present without loss of function at any level of hematologic disease in SM. Organ swelling may be stable over long periods of time without progression to aggressive systemic mastocytosis (ASM)[x].
  • Lifespan for indolent systemic mastocytosis is normal[x].
Table 2: Diagnostic criteria for smoldering systemic mastocytosis

 (2 or 3 B findings in addition to meeting criteria for systemic mastocytosis)[i]

B findings Increased mast cell burden (>30% mast cell aggregates on bone marrow biopsy and/or serum tryptase >200 ng/mL) Hypercellular marrow, signs of myelodysplasia or myeloproliferation in absence of MDS or MPN Organ swelling without deficit of organ function (hepatomegaly without ascites, palpable splenomegaly, lymphadenopathy >2 cm)

 

Natural history of smoldering systemic mastocytosis:

  • Smoldering systemic mastocytosis (SSM) is defined by increased systemic mast cell burden, presence of markers associated with progression toward ASM (B findings), and potential need for cytoreduction[xiii].
  • SSM can remain stable for many years, even decadesix. In a cohort of 22 patients with SSM, 1 transformed to acute leukemia and 3 progressed to ASM[xiv].
  • Lifespan may be shortened in SSM. A widely reported study found an average lifespan of 10 years but reported that death was often unrelated to mastocytosis and in some cases was of natural old age[xiii].
Table 3: Diagnostic criteria for aggressive systemic mastocytosis

(1 or more C finding in addition to meeting criteria for systemic mastocytosis)[i]

C findings One or more cytopenias (absolute neutrophil count <1000/µl; Hemoglobin <10g/dl; platelets <100000/µl) Hepatomegaly with ascites, elevated liver enzymes with or without portal hypertension Splenomegaly with hypersplenism Malabsorption evidenced by low albumin and weight loss Large osteolysis and/or severe osteoporosis and pathologic fractures (2 or more fractures as direct result of mast cell activity)

 

Natural history of aggressive systemic mastocytosis:

  • Aggressive systemic mastocytosis (ASM) is defined by significant organ damage and failure as a direct result of mast cell infiltrationxv. Lifespan is often significantly shortened and can be as short as three years[ix] .
  • ASM generally follows one of two paths: a slow progressing form that resembles SSM but has C findings; or a rapidly progressing form that resembles mast cell leukemia. In rapidly progressing ASM, the patient may lose the CKIT D816V mutation[ix] .
  • ASM is managed with cytoreduction but patient response is often short lived. Tyrosine kinase inhibitors and other kinase inhibitors are also used in this population[ix] .
  • In treatment resistant cases, hematopoietic stem cell transplant offers an experimental option. One study on HSCT in advanced systemic mastocytosis included seven ASM patients. 3 (43%) achieved complete remission; 3 (43%) demonstrated progression free survival at the three year mark[xv].

References:

[i] Arber DA, et al. (2016). The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia. Blood, 127(20), 2391-2405.

[ii] Minnei F, et al. (2006). Chronic urticaria is associated with mast cell infiltration in the gastroduodenal mucosa. Virchows Arch, 448(3), 262-268.

[iii] Guilarte M, et al. Diarrhoea-predominant IBS patients show mast cell activation and hyperplasia in the jejunum. Gut, 56, 203-209.

[iv] Hamilton MJ, et al. (2011). Mast cell activation syndrome a newly recognized disorder with systemic clinical manifestations. J Allergy Clin Immunol, 128, 147-152.

[v] Molderings GJ, et al. (2011). Mast cell activation disease: a concise practical guide for diagnostic workup and therapeutic options. Journal of Hematology & Oncology, 4(10), 10.1186/1756-8722-4-10

[vi] Butterfield JH, Li, CY. (2004). Bone marrow biopsies for the diagnosis of systemic mastocytosis: is one biopsy sufficient? Hematopathology, Am J Clin Pathol, 121: 264-267.

[vii] Sanchez-Munoz L, et al. (2011). Evaluation of the WHO criteria for the classification of patients with mastocytosis. Mod Pathol, 24(9), 1157-1168.

[viii] Phadia AB. ImmunoCAP® Tryptase: Clinical utility of Total Tryptase. Retrieved from: http://www.phadia.com/Global/Market%20Companies/Sweden/Best%C3%A4ll%20information/Filer%20(pdf)/ImmunoCAP_Tryptase_Clin_Util.pdf

[ix] Schwartz LB. (2006). Diagnostic value of tryptase in anaphylaxis and mastocytosis. Immunology and Allergy Clinics of North America, 26(3), 451-463.

[x] Valent P, et al. (2010). How I treat patients with advanced systemic mastocytosis. Blood, 116(26), 5812-5817.

[xi] Matito A, et al. (2013). Serum tryptase monitoring in indolent systemic mastocytosis: association with disease features and patient outcome. PLoS One, 8(10), e76116.

[xii] Lim KH, et al. (2009). Systemic mastocytosis in 342 consecutive adults: survival studies and prognostic factors. Blood, 113(23), 5727-5736.

[xiii] Pardanini A. (2013). How I treat patients with indolent and smoldering mastocytosis (rare conditions but difficult to manage). Blood, 121, 3085-3094.

[xiv] Pardanini A. (2010). WHO subvariants of indolent mastocytosis: clinical details and prognostic evaluation in 159 consecutive adults. Blood, 115, 150-151.

[xv] Ustun C, et al. (2014). Hematopoietic stem-cell transplantation for advanced systemic mastocytosis. J Clin Oncol, 32(29), 3264-3274.

[xvi] Pardanini A. (2013). Systemic mastocytosis in adults: 2013 update on diagnosis, risk stratification, and management. American Journal of Hematology, 88(7, 612-624).

[xvii] Valent P, et al. (2003). Aggressive systemic mastocytosis and related mast cell disorders: current treatment options and proposed response criteria. Leuk Res, 27(7), 635-641.

Bone involvement in ISM, SSM, SM-AHNMD and ASM: More literature review (part 3)

A 2009 paper looked at prognosis of 157 ISM patients (Escribano 2009). 27% had bone involvement, with 18% patients having osteoporosis, 6% having diffuse bone sclerosis, 4% having patchy bone sclerosis 2% having small osteolysis and 3% having pathological fracture.

A 2012 paper (van der Veer 2012) assessed the frequency of osteoporosis and osteoporotic fractures in a group of 157 ISM patients. They found 28% had osteoporosis, with 27% having osteoporosis of the lumbar spine and 1% having osteoporosis of the hip. 4% had evidence of osteosclerosis.

43% of patients under 50 years old had had at least one fracture (osteoporotic or not) and 61% of patients over 50 years old had had at least one fracture. 27% of patients had one or more vertebral fractures and 21% had non-vertebral, osteoporotic fractures. 23% of male patients under 50 had osteoporosis as well as 38% over 50. 12% of women under 50 had osteoporosis as well as 33% over 50. In total, 37% had osteoporotic fractures. In the group with comorbidities that might cause osteoporosis or fractures, 49% had osteoporotic fractures and 37% had osteoporosis. 59% ISM patients without UP had osteoporotic fractures compared to 28% with UP.

A 2013 paper (Matito 2013) looked at the association of baseline serum tryptase with disease features, including progression to SSM or ASM. 74 patients with ISM were included in the study and were followed for at least 48 months. None of them received cytoreductive therapy. Patients with an increased serum baseline tryptase slope and those without significant tryptase increase had similar prevalence of osteoporosis, patchy bone sclerosis and diffuse bone sclerosis at both presentation and end of study. However, the group with increased serum baseline tryptase was more likely to develop diffuse bone sclerosis in the time span between the beginning of the study and the end of the study (13% vs 2% without significant tryptase increase).

Among the group with low serum baseline tryptase increase, 9% had osteoporosis at the start, and 14% at the end; 5% had patchy osteosclerosis at the end; 2% had diffuse bone sclerosis at the end. None in this group progressed to SSM or ASM.

Among the group with high serum baseline tryptase increase, 10% had osteoporosis at the start, and 16% at the end; 6% had patchy osteosclerosis at the end; 13% had diffuse bone sclerosis at the end. 13% progressed to SSM and 6% to ASM.

Four patients in this study progressed to SSM after the start of the study, in a time ranging from 8-85 months. All had serum baseline tryptase of at least 200 ng/ml and had increased serum baseline tryptase slope. They also had D816V CKIT mutation in cells other than mast cells. Two of these patients progressed to ASM. Both of these patients had diffuse bone sclerosis and swelling of both the liver and spleen. The authors of this paper recommend special attention to the development of hepatomegaly and splenomegaly and diffuse bone sclerosis.

 

References:

Maurizio Rossini, et al. Bone mineral density, bone turnover markers and fractures in patients with indolent systemic mastocytosis. Bone 49 (2011) 880–885.

Theoharides TC, Boucher W, Spear K. Serum interleukin-6 reflects disease severity and osteoporosis in mastocytosis patients. Int Arch Allergy Immunol 2002;128: 344–50.

Dobigny C, Saffar JL. H1 and H2 histamine receptors modulate osteoclastic resorption by different pathways: evidence obtained by using receptor antagonists in a rat synchronized resorption model. J Cell Physiol. 1997 Oct;173(1):10-8.

Barete S, Assous N, de Gennes C, Granpeix C, Feger F, Palmerini F, et al. Systemic mastocytosis and bone involvement in a cohort of 75 patients. Ann Rheum Dis 2010;69:1838–41.

Nicolas Guillaume, et al. Bone Complications of Mastocytosis: A Link between Clinical and Biological Characteristics. The American Journal of Medicine (2013) 126, 75.e1-75.e7

van der Veer, W. van der Goot, J. G. R. de Monchy, H. C. Kluin-Nelemans & J. J. van Doormaal. High prevalence of fractures and osteoporosis in patients with indolent systemic mastocytosis. Allergy 67 (2012) 431–438.

Kushnir-Sukhov NM, Brittain E, Reynolds JC, Akin C, Metcalfe DD. Elevated tryptase levels are associated with greater bone density in a cohort of patients with mastocytosis. Int Arch Allergy Immunol. 2006;139(3):265-70. Epub 2006 Jan 30.

Matito A, Morgado JM, Álvarez-Twose I, Laura Sánchez-Muñoz, Pedreira CE, et al. (2013) Serum Tryptase Monitoring in Indolent Systemic Mastocytosis: Association with Disease Features and Patient Outcome. PLoS ONE 8(10): e76116. doi:10.1371/journal.pone.0076116

Escribano L, A lvarez-Twose I, Sanchez-Munoz L, Garcia-Montero A, Nunez R, Almeida J et al. Prognosis in adult indolent systemic mastocytosis: a long-term study of the Spanish network on mastocytosis in a series of 145 patients. J Allergy Clin Immunol 2009;124:514–521.

Bone involvement in SM (ISM, SSM, SM-AHNMD, ASM): Literature review (part 2)

There have been several publications on bone involvement in SM. Importantly, not all of these papers define SM the same way. Some define it as ISM, while others define it as ISM, SSM, SM-AHNMD and ASM. (I personally am sloppy about not specifying when I mean ISM versus when I mean any all the systemic proliferative groups. So if it’s not clear, please ask.) Another thing to be aware of is that the terminology for osteosclerosis is not consistent. It is sometimes referred to as osteocondensation (this is primarily a term used by French researchers). I have done some digging recently on this and cannot find any indication that these two terms do not represent the same phenomenon (increased deposition of bone), so if anyone knows of any papers or sources that say they are different, please let me know.

A 2010 paper (Barete 2010) defines SM as ISM, SSM, SM-AHNMD and ASM. They divided the study into two groups: Variant 1 (non-aggressive), ISM and SSM; and Variant 2 (aggressive), SM-AHNMD and ASM.

Overall (ISM, SSM, SM-AHNMD and ASM), 49% of patients had some form of bone involvement. Osteoporosis was most common, occurring in 31% of patients. 17% had a vertebral fracture. 8% had osteosclerosis. 4% had a mixed pattern, so more than one type of bone involvement. 5% had osteopenia with a previous fracture (this could be unrelated to mast cell disease, like an arm broken in a fall). Only one patient had a focal area of osteolysis with spontaneous fracture.

56% of variant 2 (aggressive) group had osteoporosis, compared to 23% of variant 1. However, when they excluded people who were classified as variant 2 based upon bone involvement, the association dropped to 17% variant 2 with osteoporosis and 23% of variant 1. Osteoporosis associated with vertebral fracture affected 48% variant 1 and 8% variant 2. Osteoporosis was also found to be associated with fewer GI symptoms, with 39% variant 1 having GI issues while 65% variant 2 did.

A total of six patients (out of a total group of 75) had osteosclerosis. One ISM, one SSM, three ASM and one SM-AHNMD patient had osteosclerosis. This translates to two in the variant 1 group and four in the variant 2 group, so twice as many in the aggressive group (ASM, SM-AHNMD) as in the non-aggressive group. 66% of patients in variant 2 with osteosclerosis had a blood count abnormality (anemia, thrombocytopenia, eosinophilia) vs 12% in variant 1. 83% of patients in variant 2 with osteosclerosis had received cytoreductive therapy vs 33% in variant 1, and higher tryptase level was associated with osteosclerosis. Overall, this means that osteosclerosis was associated with a more severe disease presentation (a patient with ISM and osteosclerosis may have a blood count abnormality), but this study does not provide any insight as to whether osteosclerosis is a marker associated with progression toward ASM or SM-AHNMD.

A 2011 paper (Guillaume 2011) assessed bone involvement in a group of CM and SM patients. In this study, SM included ISM, ASM and SM-AHNMD. 45 patients were included.  They found one patient with osteolysis, eight with osteocondensation (a form of osteosclerosis), four with a mixed pattern and three with fractures. They found no association between the presence of radiologic lesions (lesions detected by imaging techniques) and severity (here classified as non-aggressive: ISM and CM, and advanced: ASM and SM-AHNMD).

This study also looked at chemical markers used for bone remodeling. They found that markers associated with both bone resorption and bone formation were higher in mastocytosis patients than in the general population. The higher levels were thought to represent increased number of osteoblasts and osteoclasts due to the increase in mast cells. Osteoprotegerin was also higher in mastocytosis patients. This is a protein released by osteoblasts that regulates the activity of osteoclasts. Levels of C-telopeptide were significantly higher in patients with SM-AHNMD or ASM than in patients with ISM or CM.

A 2011 paper (Rossini 2011) investigated the relationship between tryptase and bone turnover markers (bone specific alkaline phosphatase, C-telopeptide, osteocalcin) in ISM patients. A total of 82 patients were enrolled in the study. 36% had bone involvement. 20% had osteoporosis, with 18.7% found in the spine and 2.5% at the hip. Five patients had a history of bone breaks outside of the spine. 27 patients had vertebral fractures. Two patients had osteosclerotic features and also had particularly high tryptase levels. Another study previously reported that high tryptase can be associated with increased bone density (Kushnir-Sukhov 2006).

This study had a large amount of ISM patients without skin lesions (55%). A very important finding of this particular study was that ISM patients without skin lesions are at the same risk for osteoporosis. As lesions are often one of the more identifiable markers of mastocytosis, the author raises the very valid point that osteoporosis may in some people be the only sign of latent ISM.

This paper reported that “diffuse osteosclerosis associated with SM is not a[n] “osteopetrosis-like osteopathy”, as previously reported, but a skeletal disease characterized by increased bone turnover.” This is important, as they have previously been equated for lack of distinction. The author further notes that the “pathophysiology of SM-related osteosclerosis remains obscure, although it is known that MCs can exert a direct stimulatory effect on osteoblast proliferation, recruitment, and activity.”

This study found that bone mineral density and serum tryptase did not correlate with the serum markers of bone turnover. However, it did find that ISM patients with osteosclerosis had higher tryptase and bone turnover markers (bone specific alkaline phosphatase and C-telopeptides of type I collagen) than ISM patients with other types of bone involvement.

(Literature review continued tomorrow)

References:

Maurizio Rossini, et al. Bone mineral density, bone turnover markers and fractures in patients with indolent systemic mastocytosis. Bone 49 (2011) 880–885.

Theoharides TC, Boucher W, Spear K. Serum interleukin-6 reflects disease severity and osteoporosis in mastocytosis patients. Int Arch Allergy Immunol 2002;128:344–50.

Dobigny C, Saffar JL. H1 and H2 histamine receptors modulate osteoclastic resorption by different pathways: evidence obtained by using receptor antagonists in a rat synchronized resorption model. J Cell Physiol. 1997 Oct;173(1):10-8.

Kushnir-Sukhov NM, Brittain E, Reynolds JC, Akin C, Metcalfe DD. Elevated tryptase levels are associated with greater bone density in a cohort of patients with mastocytosis. Int Arch Allergy Immunol. 2006;139(3):265-70. Epub 2006 Jan 30.

Barete S, Assous N, de Gennes C, Granpeix C, Feger F, Palmerini F, et al. Systemic mastocytosis and bone involvement in a cohort of 75 patients. Ann Rheum Dis 2010;69:1838–41.

Nicolas Guillaume, et al. Bone Complications of Mastocytosis: A Link between Clinical and Biological Characteristics. The American Journal of Medicine (2013) 126, 75.e1-75.e7

van der Veer, W. van der Goot, J. G. R. de Monchy, H. C. Kluin-Nelemans & J. J. van Doormaal. High prevalence of fractures and osteoporosis in patients with indolent systemic mastocytosis. Allergy 67 (2012) 431–438.

Bone involvement in SM (ISM, SSM, SM-AHNMD, ASM): Clarifications (part 1)

One of the more nuanced aspects of mastocytosis is how it affects bone structure. Previously, it was thought that only patients with systemic mastocytosis experienced bone pain, and that bone pain was always a function of increased proliferation in the marrow. This no longer appears to be the case. Some patients with non-proliferative mast cell disease have been found to experience bone pain, likely as a result of mediator activity on the outside of the bone. In particular, histamine can be very irritating to the cells on the outside of the bone.

Generally speaking, bone cells work like this:

Osteoblasts make new bone. Osteoclasts eat away (resorb) at bone so that new bone can be put in that place. When these processes aren’t balanced, you develop bone conditions.

In osteosclerosis, your body is making new bone faster than it can resorbed. In osteoporosis, your body is resorbing bone faster than new bone is made.   In osteolysis, your body is also resorbing bone faster than new bone is made, but to a much larger extent than usually seen in osteoporosis. Both osteoporosis and osteolysis can cause pathologic fractures, meaning that because your bone is weak from osteoporosis or osteolysis, the bone breaks.

Bone involvement in systemic mastocytosis is important because the type of bone involvement present can be used to stage the disease. Specifically, certain types of bone involvement can cause a person with indolent or smouldering systemic mastocytosis to be reclassified as aggressive systemic mastocytosis (ASM). Osteolysis (in which bone is eaten away) is a marker for ASM. If you have ISM or SSM and are found to have a large osteolytic lesion, you now have ASM.

More confusing is the relationship of osteoporosis to ASM. If you have ISM or SSM AND you have osteoporosis AND you have multiple fractures due to the severity of the osteoporosis (known as pathologic fractures), you are classified as having ASM. There is some debate in the community as to whether or not osteoporosis with successive pathologic fractures is a true indication of ASM. However, it is currently included in the diagnostic guidelines, and so if you meet this criteria while also having ISM or SSM, then you are classified as having ASM.

But I want to be very clear about something: the osteoporosis is NOT the factor that classifies someone as having ASM. It is the MULTIPLE FRACTURES as a result of bone disease that classifies someone as having ASM. So if you have SSM and are diagnosed with osteoporosis and have a single vertebral fracture as a result of osteoporosis, you are NOT classified as having ASM. It is easier I think to consider this “bone involvement” criterion of ASM as osteolysis or multiple fractures due to bone deterioration.

SM is well known as a possible risk factor for osteoporosis. This has been attributed by different groups to either infiltration of bone by mast cells or release of mediators, including histamine, heparin and tryptase. IL-6 levels were also shown to be proportional to disease severity and osteoporosis in mastocytosis patients (Theoharides 2002). Histamine regulates bone resorption by osteoclasts via H1 and H2 receptors (Dobigny 1997). In bone biopsies of osteoporotic patients, the number of osteoclasts is sometimes elevated and sometimes normal.

Up next: literature review of studies on bone involvement in ISM, SSM, SM-AHNMD, and ASM.

 

References:

Maurizio Rossini, et al. Bone mineral density, bone turnover markers and fractures in patients with indolent systemic mastocytosis. Bone 49 (2011) 880–885.

Theoharides TC, Boucher W, Spear K. Serum interleukin-6 reflects disease severity and osteoporosis in mastocytosis patients. Int Arch Allergy Immunol 2002;128: 344–50.

Dobigny C, Saffar JL. H1 and H2 histamine receptors modulate osteoclastic resorption by different pathways: evidence obtained by using receptor antagonists in a rat synchronized resorption model. J Cell Physiol. 1997 Oct;173(1):10-8.

Barete S, Assous N, de Gennes C, Granpeix C, Feger F, Palmerini F, et al. Systemic mastocytosis and bone involvement in a cohort of 75 patients. Ann Rheum Dis 2010;69:1838–41.

Nicolas Guillaume, et al. Bone Complications of Mastocytosis: A Link between Clinical and Biological Characteristics. The American Journal of Medicine (2013) 126, 75.e1-75.e7

van der Veer, W. van der Goot, J. G. R. de Monchy, H. C. Kluin-Nelemans & J. J. van Doormaal. High prevalence of fractures and osteoporosis in patients with indolent systemic mastocytosis. Allergy 67 (2012) 431–438.

Mast cell mutations: TET2 and mutation profiles of aggressive subtypes

TET2 (Tet methylcytosine dioxygenase 2) is found to be mutated in 20.8-29% of SM patients. Of note, dozens of mutations have been identified in this gene, including missense, nonsense, frameshift and deletion mutations. These mutations cause formation of a defective and less active TET2 enzyme. TET2 is located at chromosome 4q24 and mutations at this location are associated in both MPN and MDS conditions.

TET2 is involved in DNA methylation and demethylation, although the exact nature of this involvement is not clear. When a methyl group is added to a cytosine at a specific place in front of a gene, the gene is turned off and is not expressed. This is called “methylation.” TET2 adds a hydroxyl group to 5-methylcytosine, but it is not well understood if this turns the gene off. TET2 may also be involved in demethylating DNA, or removing those specific methyl groups. It has been shown to be involved with DNA demethylation during bone development.

One study looked at the mutational profiles of patients with various forms of SM, including ISM, SSM, SM-AHNMD, ASM and MCL, all of whom were positive for CKIT D816V mutation. 15/39 had a TET2 mutation. None of those patients had ISM or SSM. Of those with an aggressive form and a TET2 mutation, 67% had more than one TET2 mutation.

In this study, 24/27 patients with advanced SM (SM-AHNMD, ASM, MCL) had mutations beyond the D816V mutation. 5/5 SM-AHNMD patients and 19/22 ASM or MCL patients had multiple mutations (CKIT and something else.) In contrast, only 3/12 ISM or SSM patients had additional mutations. In advanced SM, 78% had at least 3 mutations, and 41% had at least 5.

These mutational profiles have clear implications clinically. 96% patients with major blood abnormalities (anemia <10 g/dL and/or thrombocytopenia < 100 x 10e9/L in addition to monocytosis > 1 x 10e9/L and/or eosinophilia >10%) had at least one additional molecular mutation regardless of SM subtype.

Advanced SM patients in this study all had one of the following multiple mutation profiles: 26% KIT-TET2-SRSF2, 18% KIT-SRSF2-RUNX1, 13% KIT-TET2-CBL, 10% KIT-SRSF2-ASXL1 10%, and 10% KIT-TET2-ASXL1. Patients with advanced SM (and therefore multiple mutations) were also found to be significantly older (68 years of age on average) than those with just the CKIT mutation (48 years of age on average.)

Having a TET2 mutation seems to predispose myeloid cells to become neoplastic later in life. It is important to distinguish that the TET2 mutation seems to “allow” this transformation rather than causing it. In mice who don’t have the TET2 gene and thus don’t have the TET2 enzyme, stem and progenitor cells have trouble maintaining balance and spontaneously become neoplastic later in life. In TET2 deficient cells, mast cells with D816V mutation show increase in proliferation and survival as opposed to those without with normal TET2 levels. Presence of TET2 in addition to the presence of CKIT D816V mutation is associated with more aggressive forms of SM (including ASM, MCL and SM-AHNMD.)

 

References:

Damaj, G., Joris, M., Chandersris, O., Hanssens, K., Soucie, E., Canioni, D., et al., 2014.ASXL1 but not TET2 Mutations Adversely Impact Overall Survival of PatientsSuffering Systemic Mastocytosis with Associated Clonal Hematologic Non-Mast-Cell Diseases. PLoS ONE 9 (1), e85362.

Schwaab, J., Schnittger, S., Sotlar, K., Walz, C., Fabarius, A., Pfirrmann, M., et al., 2013.Comprehensive mutational profiling in advanced systemic mastocytosis. Blood122 (October (14)), 2460–2466.

Soucie, E., Hanssens, K., Mercher, T., Georgin-Lavialle, S., Damaj, G., Livideanu, C.,et al., 2012. In aggressive forms of mastocytosis. TET2 loss cooperates with c-KITD816V to transform mast cells. Blood 120 (December (24)), 4846–4849.

Soucie, E., Brenet, F., Dubreuil, P. Molecular basis of mast cell disease. Molecular Immunology 63 (2015) 55-60.

Progression of mast cell diseases: Part 1

Among mast cell patients, we generally assume that a designation of SM means indolent systemic mastocytosis (ISM.) However, in research papers, this term can mean ISM, SSM, ASM or MCL. Advanced SM usually means ASM or MCL. These terms generate a lot of confusion in the patient population. When reading a paper, abbreviations are usually defined on the first page or within the introduction. It is important to check on what the researchers are using the term SM for.

As an example, let’s look at this really alarming quote to someone who thinks SM means ISM:

“The life expectancy of SM patients was shorter relative to age- and sex-matched controls. As initially observed by Travis et al, survival decreased rapidly after diagnosis: to 60% at 3 years, with a subsequent slower decline to 50% at 5 years. Beyond 5 years, the slope of the survival curve was similar to that of the control population. This observation confirms that the deaths in SM patients within the first 3 (and up to 5) years after diagnosis.” (Lim 2009)

In this paper, SM meant ISM, SM-AHNMD, SSM, ASM and MCL. When you average those survival rates together, you get a sharp decline in survival for the first five years. After that, it returns to normal, because most of the ASM and MCL patients in that study died by that time.

 

I get asked A LOT about whether or not ISM is progressive. I see a lot of people describe it as progressive. In medicine, progression usually means moving from one diagnostic category to a more serious one (like ISM to SSM.) However, a lot of patients use this term to mean a worsening of symptoms or disability while staying in the same diagnostic category (like ISM with mild daily symptoms to ISM with severe daily symptoms). Those are two different things. I’m going to answer both.

 

What is the life expectancy with ISM?

It’s normal.

“Patients with ISM have a favorable prognosis. These patients may suffer from mediator-release symptoms, but do not suffer from significant organopathy caused by MC infiltration.” (Valent, 2003)

In a study of 159 patients, 2.2% ± 1.3% died within five years of diagnosis, and 11% ± 5.9% died within twenty five years of diagnosis. “The majority of deaths in this ISM cohort were unrelated to mastocytosis.” (Pardanini 2013)

In a study of 342 patients, ISM was the largest subgroup with 159 patients.  They were significantly younger at presentation (median age 49 years.) “Overall median survival was not significantly different than that of the age and gender matched control population. Advanced age was the primary determinant of inferior survival.” (Pardanini 2013)

 

Will my ISM symptoms get worse with time?

There is really no way to know. In some people, they are stable, while in others, they fluctuate. However, mediator release symptoms (degranulation symptoms) are known to be more common in ISM than ASM and MCL.

“ISM patients can be highly symptomatic; in one study, 70% reported at least some degree of functional limitation, of which 17% reported severe limitation.” (Pardanini 2013)

“The type and severity of symptoms were independent of disease classification (CM vs SM), KITD816V status, and serum tryptase level.” (Pardanini 2013)

 

If my ISM symptoms get worse, does that mean I am progressing to a more severe category, like SSM, ASM or MCL?

No.

“One important aspect in this regard is that mediator-related symptoms per se are not indicative of aggressive mastocytosis unless accompanied by C-findings.” (Valent 2003)

“Moreover, organomegaly per se is not necessarily indicative of aggressive SM.” (Valent 2003)

“In fact, in a group of patients with SM, organomegaly is recorded over many years without impairment of organ function or development of C-findings.” (Valent 2003)

“The type and severity of symptoms were independent of disease classification (CM vs SM), KITD816V status, and serum tryptase level.” (Pardanini 2013)

 

References:

Pardanini, Animesh. How I treat patients with indolent and smoldering mastocytosis (rare conditions but difficult to manage.) 2013; Blood: 121 (16).

Pardanini, Animesh. Systemic mastocytosis in adults: 2013 update on diagnosis, risk stratification, and management. 2013; American Journal of Hematology: 88 (7).

Pardanini, Animesh. Prognostically relevant breakdown of 123 patients with systemic mastocytosis associated with other myeloid malignancies. 2009; Blood: 114 (18).

Lim, Ken-Hong, et al. Systemic mastocytosis in 342 consecutive adults: survival studies and prognostic factors. 2009; Blood: 113 (23).

Valent, Peter, et al. How I treat patients with advanced systemic mastocytosis. 2010; Blood: 116 (26).

Matito, Almudena, et al. Serum tryptase monitoring in indolent systemic mastocytosis: association with disease features and patient outcome. 2013; PLOS One.

Sperr, Wolfgang. Diagnosis, progression patterns and prognostication in mastocytosis. 2012; Expert Review of Hematology: 5 (3): 261-274.

Valent, Peter, et al. Aggressive systemic mastocytosis and related mast cell disorders: current treatment options and proposed response criteria. 2003; Leuk Res 27 (7): 635-41.

Hauswirth, Alexander, et al. Response to therapy with interferon alpha-2b and prednisolone in aggressive systemic mastocytosis: report of five cases and review of the literature. 2004; Leuk Res 28 (3): 249-257.

Language matters: Mast cell terminology

This is by no means a comprehensive list – just a review on definitions of some commonly confused terms.

Acute: This word gets used a lot when people mean “severe.” Acute does not mean severe. It means sudden onset or having a short, limited course. For example, stage III anaphylaxis is an acute complication of mast cell disease. Its symptoms come on suddenly, require immediate treatment, and once treated, resolves. (I am not referring to the after effects of anaphylaxis – just the emergency and treatment.) In a medical sense, acute is the opposite of chronic.

Chronic: Long term, occurs all the time, is expected to occur forever. I have mast cell disease and am chronically ill. I have acute anaphylactic emergencies.

Progressive: Getting worse or will get worse. This term gets used loosely by patients to mean that their symptoms get worse. Medically speaking, this generally refers to progression of disease from one stage to the next, like SM to ASM. SM and MCAS are not inherently progressive diseases. People who have progressed from SM to SSM or ASM have progressive disease.

 

Systemic symptoms: Any symptoms that do not involve the skin. Can be present in cutaneous mastocytosis or MCAS. So diarrhea is a systemic symptom. Tachycardia is a systemic symptom. Systemic symptoms do not mean you have SM.

Systemic mastocytosis: the diagnosis you receive if you meet either the major criterion listed subsequently and at least 1 of the 4 minor criteria, or at least 3 minor criteria if the major criterion is not met:

Major criterion

Multifocal, dense infiltrates of mast cells (≥15 mast cells in aggregates) detected in sections of bone marrow and/or other extracutaneous organ(s)

Minor criteria

In biopsy sections of bone marrow or other extracutaneous organs, >25% of the mast cells in the infiltrate are spindle-shaped or have atypical morphology, or, of all mast cells in bone marrow aspirate smears, >25% are immature or atypical

Detection of an activating point mutation at codon 816 of KIT in bone marrow, blood, or other extracutaneous organ

Mast cells in bone marrow, blood, or other extracutaneous organ express CD2 and/or CD25 in addition to normal mast cell markers

Serum total tryptase persistently exceeds 20 ng/mL (unless there is an associated clonal myeloid disorder, in which case this parameter is not valid)

The diagnosis of SM is unrelated to the symptoms the patient experiences. Some SM patients have no symptoms. Some have severe symptoms.

Systemic symptoms ≠ systemic disease (SM)

 

Aggressive symptoms: Frequent or severe symptoms, which may be life threatening.

Aggressive disease: Doctors sometimes use this term to mean a quick progression of symptoms or rapid change in quality of life.

Aggressive systemic mastocytosis: A diagnosis that indicates multiple organ infiltration and damage by mast cells. Lifespan is significantly shortened in many patients. It is diagnosed by already meeting the criteria for SM and then also having at least one C finding, listed here:

Bone marrow dysfunction manifested by one or more cytopenia (ANC < 1.0 × 109/l, Hb < 10 g/dl, or platelets < 100 × 109/l), but no frank non-mast cell haematopoietic malignancy

Palpable hepatomegaly with impairment of liver function, ascites and/or portal hypertension

Skeletal involvement with large-sized osteolysis and/or pathological fract

Palpable splenomegaly with hypersplenism

Malabsorption with weight loss due to GI mast cell infiltrates

Aggressive symptoms and aggressive disease ≠ aggressive systemic mastocytosis (ASM)

 

Smoldering systemic mastocytosis (SSM): A progression from SM with markers that indicate likelihood of developing ASM. Diagnosed if two or more of the following B findings are present with previous diagnosis of SM:

Bone marrow biopsy showing > 30% infiltration by mast cells (focal, dense aggregates) and/or

serum total tryptase level > 200 ng/ml

 

Signs of dysplasia or myeloproliferaion in non-mast cell lineage, but insufficient criteria

for definitive diagnosis of a haematopoietic neoplasm by WHO, with normal or only slightly

abnormal blood counts

 

Hepatomegaly without impairment of liver function, and/or palpable splenomegaly without

hypersplenism, and/or palpable or visceral lymphadenopathy

 

MCAD, MCAS and the hierarchy of mast cell disease classifications

I have seen several posts recently expressing confusion about various mast cell diagnoses so I figured I would put up a post to clear things up.
Mast cell activation disorder (MCAD) is a catch-all term for mast cell disease (MCD.)  MCAD and MCD can be used interchangeably.  So if you have any mast cell disease, you have MCAD.  If you have SM, you have MCAD, because SM is a type of MCAD.  If you have UP, you have MCAD, and so on.  MCAD is an umbrella term.  It is non-specific.  It is similar to being told that you have heart disease when you have mitral valve prolapse.  It is true, but it is not precise enough to give all information needed to treat effectively.
Mast cell activation syndrome (MCAS) is the diagnosis you get if you do not meet the criteria for any of the defined mast cell diseases, but have mast cell mediator related symptoms.  You cannot have MCAS and another mast cell disease because, by its definition, MCAS is ONLY diagnosed if you do NOT meet the criteria for any other mast cell disease.  You cannot have UP and MCAS.  You cannot have SM and MCAS.  I think some people think that MCAS means you have mediator related symptoms.  This is not the case.  You can have mediator related symptoms with pretty much any mast cell disease. 
A paper was published a few years ago by a doctor who considers mast cell activation symptoms to be due exclusively to proliferation (like in SM.)  He wrote a paper that says that MCAS is found in people with SM.  This paper sort of confused the issue for a lot of people.  However, the mast cell community (including researchers and prominent doctors) do not consider this to be the case.  They agree that you cannot have SM and MCAS.
Also confusing is the fact that mast cell activation (MCA) is NOT the same as MCAS.  MCA just means that your mast cells are activated, which occurs in any mast cell disease.  MCA is not a diagnosis, it is a symptom.  So you can have MCA in SM.  But you still can’t have MCAS in SM.
So if you have SM and have lots of mediator related symptoms, you have SM.  If you want to speak broadly, you have SM.
If you test negative for SM and have no CM, but have mast cell symptoms and elevated mast cell markers, you have MCAS. 
If you have UP and then later develop SM, you have SM with skin involvement, or SM with UP. 
If you have UP or TMEP and have lots of mediator related systemic symptoms, you do NOT have UP and MCAS.  You have UP.  UP and TMEP (forms of CM) can cause systemic symptoms.  But you cannot have MCAS because you can only have MCAS if you do not meet the criteria for another mast cell disease.
Let’s review.
If you have UP: you have UP, you have CM, you have MCAD.
If you have TMEP: you have TMEP, you have CM, you have MCAD.
If you have SM: you have SM, you have MCAD.
If you have SM with UP: you have SM with skin involvement, you have UP, you have MCAD.
If you have SM with TMEP: you have SM with skin involvement, you have TMEP, you have MCAD.
If you have SM-AHNMD: you have SM-AHNMD, you have MCAD.
If you have ASM: you have ASM, you have MCAD.
If you have MCL: you have MCL, you have MCAD.

If you have MCAS: you have MCAD.

Reference:
Molderings GJ, Brettner S, Homann J, Afrin LB. Mast cell activation disease: a concise practical guide for diagnostic workup and therapeutic options. J. Hematol. Oncol.2011; 4:10-17.

The question I get asked the most

Whether or not SM is cancer is, by far, the question I get asked the most.  Because I get asked so often, I have done a lot of digging on this topic in the last few months.  Here’s what I found.

On the surface, from a biological point of view, SM looks like cancer.  It is characterized by excessive, improper cell growth.  It can cause organ infiltration and damage.  Over 90% of patients have a mutation in the CKIT gene, which is a proto-oncogene.  A proto-oncogene is a gene that becomes an oncogene when mutated.  An oncogene is a gene that contributes to cancer.  CKIT mutations can lead to gastrointestinal stromal tumors (GIST), melanoma, acute myeloid leukemia and, of course, mast cell disease.  So if SM has unregulated cell growth and a mutation in a proto-oncogene, that makes it cancer, right?
The World Health Organization (WHO), an organization I generally consider to know what they are doing, says it doesn’t.  To find out exactly why, I talked to a pathologist familiar with mast cell disease.  This is what she said:
“All cancers are neoplasms, but not all neoplastic cells are cancerous.  It is cancerous when the cells grow out of control.  In mastocytosis, even if you do nothing (meaning take no medications designed to kill off the mast cells), most of the time, the prognosis is very good because the cells are not growing that much.  Not like a cancer.  The other thing is when the cells invade other organs and the bloodstream and damage the organs.  When it is widespread and damaging, it is malignant.”
The majority of people with systemic mastocytosis have indolent disease, for which the life expectancy is normal, usually without any kind of therapy to kill off mast cells.  So if we follow the guidelines laid out above, SM is not cancer.   It is a myeloproliferative neoplasm (MPN.)
I know some people with ASM identify as having cancer.  ASM has a lot more features we typically associate with cancer, so I think that’s fine.  And MCL, obviously, is leukemia.
There is some terminology that gets thrown around incorrectly and I think it scares people who don’t understand that the wrong terms are being used.  One of them is chemo.  People with more aggressive types of mast cell disease may need chemo drugs.  People sometimes use the term incorrectly to reference more common treatments.  If you’re a rookie, I can see how you might get scared thinking that lots of people with indolent disease are on chemo.
Another term is compassionate use.  Compassionate use is the use of an experimental drug outside of a clinical trial.  It is generally allowed only when the person has no other treatment options and is gravely ill.  I have seen some people use it when discussing patient assistance programs, in which a pharmaceutical company will distribute a drug to a patient at a significant discount or at no cost.  They are not the same thing.
In the last few months, I have noticed that some people with SM will tell people that they have a “rare kind of leukemia.”  This is not accurate.  With the obvious exception of MCL, mast cell disease is not leukemia.  SM is a blood disorder. 
I think that part of why some people with mast cell disease say they have leukemia is because they want the sort of empathy given to cancer patients.  I understand that.  I wrote a whole post about how I hate when people say, “At least it’s not cancer.”  But it’s important to remember that cancer has two entities: the medical, biological aspect of the disease, and the social construct.  When you have ISM and you tell someone you have leukemia, their first thought is that you could die from it.  Mast cell disease is scary enough with scaring everyone around you extra with misinformation. 
I know that it’s frustrating that people know what cancer is and they probably don’t know what mast cell disease is.  And to be clear, I’m not talking about an offhand comment you make to some stranger asking you why you have a port at the grocery store to get them to go away.  I’m talking about the people who are actually in your life.  (I’m also obviously not referring to the SM-AHNMD people, who may very well have leukemia in addition to SM.)  If our mission is to educate people, stuff like this matters.  The words we use  matter.  A lot.  
I’m aware that this post is probably going to make some people angry, and that’s fine.  You can feel however you want to feel.  But I’m getting enough questions about this from people who are really worried, so I feel it’s important to set the record straight.

In which I answer your questions (part 1)

One of the things I like about this blog is that it shows me what search terms people use that lead them to finding this blog.  So since I’m going to answer some email questions this week, I figured I’d address some of the topics people search for as well.

“Bone marrow biopsy and mcas”

This is a big one.  Mast cell patients generally get bone marrow biopsies when SM is suspected.  Most of the time, for MCAS patients, the biopsy comes back normal, which rules out SM.  However, occasionally, it comes back with some findings but not enough for an SM diagnosis.  So what do you have then?
Generally speaking, you have MMAS (monoclonal mast cell activation syndrome.)  These patients have bone marrow biopsies that are negative for dense infiltrates, but positive for CD25 receptor expression and/or the D816V CKIT mutation. 
I know of two instances in which patients had bone marrow biopsies that were positive for dense infiltrates but they had normal tryptases, normal receptor expression, no D816V mutation, and no spindled mast cells.  So what do you have then?  Beats me.  Of these two patients, one has a diagnosis of MCAS and the other has a diagnosis of MMAS. (And if we’re being picky, neither of them have known systemic reactions to bee stings.)  My guess is that if they had repeat biopsies, they would eventually find spindled cells and CD2/CD25 expression.  I think they are both probably very early in their diseases and we just caught it while it was developing.  

“Bone pain aggressive mastocytosis”
Aggressive systemic mastocytosis is defined as systemic mastocytosis with at least one C finding: low blood cell count; impaired liver function; free fluid in the abdomen; high pressure in the vessels connecting the liver and digestive organs; large osteolytic lesions and/or pathological fractures; impaired splenic function; malabsorption with weight loss; low serum albumin. 
Mast cells are involved in bone loss and osteolysis and/or fractures causes by osteolysis are not uncommon in ASM.  Mast cells release factors associated with bone resorption, bone formation and bone remodeling.  Having more mast cells speeds up these processes. 
Conventional wisdom has long held that bone pain in mastocytosis patients came from inside the bone, where too many mast cells inhabited the marrow.  However, consistent reports of bone pain from patients with non-proliferative disease (MCAS) indicate that this may not be true.  In particular, histamine is known to be irritating to osteocytes (bone cells) and may be causing pain from outside the bones. 

“Effects of systemic mast cell disease”
This is more loaded than the other topics because it is so wide reaching.  Regarding symptoms, it can cause low blood pressure, rapid heart beat, flushing, rashes, hives, itching, abdominal pain, nausea, vomiting, diarrhea (or constipation), numbness, tingling, headaches, sinus pain, swelling, coughing, difficulty breathing and more.  Regarding long term damage, mast cell disease can cause organ damage due both to mast cell infiltration and the effects of anaphylaxis and mast cell mediators.  Regarding lifestyle and such, mast cell disease can restrict your activities, your ability to work and affect your relationships with others.  I have dozens of entries in this blog regarding these topics; if you have specific questions, please let me know.

“How to activate mast cells”
If you have mast cell disease, unfortunately, activating mast cells is not hard.  Common triggers include sunlight, heat, pressure, exercise.  stress.  Common food triggers include soy, alcohol, vinegar, tomatoes, and like a million other things.  I use the low histamine diet described by the Canadian Mastocytosis Society and have found it to be pretty accurate for me.  That said, everyone is different and triggers are super individual.  I just blew my nose too hard and started degranulating.  Activating mast cells is not so hard.

“Mast cell activation disorder prognosis”
Every reliable source reports that patients with mast cell activation disorder have normal life expectancies.  The data looks good to me.  If you think I’m a reliable source, that’s also what I’m reporting. 

“Mast cell and high heart rate”
Tachycardia (heartbeat over 110 bpm) is a common symptom for mast cell patients.  When mast cells degranulate, the histamine released causes blood vessels to leak fluid into the tissues and out of the blood stream.  This lowers the blood pressure.   The body responds with “reflex tachycardia.”  This means that your heart starts beating faster in response to the drop in blood pressure.
Many mast cell patients also have POTS, which causes tachycardia when moving to a standing position.  My POTS is managed effectively with fluid infusions and a conscious effort to not stand up quickly.
I have a PICC line and about a month after I had it placed, I started having really bad tachycardia at night.  I mentioned it to my infusion nurse who told me that this can be a sign that the end of the PICC line is too close to a heart valve, which can increase heart rate in response.  She pulled my line out about a centimeter and the problem went away.  Not exactly mast cell disease related but I know a lot of us have central lines so I figured it was worth mentioning.