MCAS: Differing criteria among experts

What criteria you have to meet to be diagnosed with MCAS depends on which doctor you see – even the experts don’t agree.

Molderings, Afrin 2011 Akin, Valent, Metcalfe 2010 Valent, Akin, Castells, Escribano, Metcalfe et al 2012
MCAD (umbrella term including both MCAS and SM) diagnosed if both major criteria, or one major criterion and one minor criterion, are present; following bone marrow biopsy, diagnosis is narrowed down to either SM or MCAS MCAS diagnosed if all criteria are met MCAS diagnosed if all criteria are met

Major Criteria

Multifocal of disseminated dense infiltrates of mast cells in bone marrow biopsies and/or in sections of other extracutaneous organ(s) (GI tract biopsies; CD117-, tryptase- and CD25- stained)
Episodic symptoms consistent with mast cell mediator release affecting ≥2 organ systems evidenced as follows:
  1. Skin: urticaria, angioedema, flushing
  2. Gastrointestinal: nausea, vomiting, diarrhea, abdominal cramping
  3. Cardiovascular: hypotensive syncope or near syncope, tachycardia
  4. Respiratory: wheezing
  5. Naso-ocular: conjunctival injection, pruritus, nasal stuffiness
Typical clinical symptoms
Unique constellation of clinical complaints as a result of a pathologically increased mast cell activity (mast cell mediator release symptom) A decrease in the frequency or severity or resolution of symptoms with antimediator therapy: H1– and H2-histamine receptor inverse agonists, antileukotriene medications (cysteinyl leukotriene receptor blockers or 5-lipoxygenase inhibitor), or mast cell stabilizers (cromolyn sodium) Increase in serum total tryptase by at least 20% above baseline plus 2 ng/ml during or within 4 h after a symptomatic period
  Evidence of an increase in a validated urinary or serum marker of mast cell activation: documentation of an increase of the marker to greater than the patient’s baseline value during a symptomatic period on ≥2 occasions or, if baseline tryptase levels are persistently >15 ng, documentation of an increase of the tryptase level above baseline value on 1 occasion. Total serum tryptase level is recommended as the marker of choice; less specific (also from basophils) are 24-hour urine histamine metabolites or PGD2 or its metabolite 11-β-prostaglandin F2. Response of clinical symptoms to histamine receptor blockers or MC-targeting agents e.g. cromolyn
  Rule out primary and secondary causes of mast cell activation and well-defined clinical idiopathic entities

Minor Criteria

Mast cells in bone marrow or other extracutaneous organ(s) show an abnormal morphology (>25%) in bone marrow smears or in histologies
Mast cells in bone marrow express CD2 and/or CD25
Detection of genetic changes in mast cells from blood, bone marrow or extracutaneous organs for which an impact on the state of activity of affected mast cells in terms of an increased activity has been proved
Evidence of a pathologically increased release of mast cell mediators by determination of the content of:

  1. Tryptase in blood
  2. N-methylhistamine in urine
  3. Heparin in blood
  4. Chromogranin A in blood
  5. Other mast cell specific mediators (leukotrienes, PGD2)

1 Response

  1. Sutida June 15, 2015 / 2:50 pm

    Hi Lisa!
    Afrin’s (et al) got a new diagnostic tool published (2014). It’s open access here: http://www.wjgnet.com/2218-6204/pdf/v3/i1/1.pdf You’ve probably already seen it but I thought I’d mention it just in case. The weight questionnaire starts on page 7. I didn’t think the MCAS/MCAD mould fit me at all before I answered the questionnaire and scored 15 without even having any of the testing done. A good preliminary self-evaluation tool to help decide whether or not it might be worth pursuing a diagnosis! 🙂

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