Chronic urticaria and angioedema: Part 2

CU lesions are swollen pink or red wheals, of variable size, often with surrounding redness. They are generally itchy rather than painful or burning. Angioedema is not itchy, brawny, of a non-pitting quality with indistinct margins and without redness.

There are a number of chronic urticaria and angioedema (CU) subsets that are triggered by environmental sources. These are called physical urticarias.

In aquagenic urticaria, patients develop hives after contact between water and the skin. Temperature is not a factor in this type of urticaria. The hives are generally “pinpoint”, measuring 1-3mm. This is confirmed by applying a water compress at near body temperature to the skin of the upper body for 30 minutes.

Cholinergic urticaria also causes pinpoint hives, but these hives are surrounded by large flare reactions as a result of increased body temperature. Exercise, sweating, emotional stress, hot baths and showers are all frequent triggers of this subtype. Cholinergic urticaria can be benign or life threatening. Testing involves exercise or hot water immersion as these activities raise the core body temperature.

Cold urticaria results in hiving when the skin is exposed to a cold source. Patients may have systemic reactions in the event of full body exposure to the cold (swimming in cold water, etc). This is tested by placing an ice cube on the patient’s skin and waiting for a reaction, which occurs when the skin starts to warm.

Delayed pressure urticaria/angioedema presents as swelling, which may be painful, after the skin is exposed to pressure. While 4-6 hours is a more typical duration for symptoms to present, in some patients it can take 12-24 hours. Working with tools, sitting on a bench, wearing tight clothing, and carrying a heavy purse are all representative triggers. Testing for this subtype involves placing a 15 lb weight on the patient’s shoulder for 10-15 minutes, then waiting for response. Angioedema at the site that evolves following this test is considered a positive test, regardless of whether or not weals are present. This type can be difficult to treat.

Dermatographia is the most common type of physical urticaria. 2-5% of the general population have dermatographia.   Stroking the skin firmly causes a weal and flare reaction where the skin was touched. It does not usually require treatment.

Exercise induced anaphylaxis has two types: those in whom anaphylaxis in provoked strictly by exercise, and those in whom anaphylaxis is triggered when a specific food is consumed prior to exercise. Cholinergic urticaria can also be triggered by exercise, so it is important to distinguish between the two. Exercise anaphylaxis can only be triggered by exercise, whereas cholinergic urticaria results if the patient becomes too hot. People with exercise induced anaphylaxis need to carry epipens and must not exercise alone as reactions can be severe.

Solar urticaria is the development of hives when the skin is exposed to sunlight, generally within minutes. Solar urticarial is further divided in subtypes based upon which wavelengths of light are triggering to the patient. Testing involves lightbox exposure to isolated wavelengths of light. It is distinct from polymorphous light eruption, in which onset is often delayed and can last for days. It can cause papules, papulovesicles and plaque manifestations on the skin.

Recall urticaria is hiving at the site of a previous sting or injection when exposed again to the same trigger.

Vibratory angioedema causes itching and swelling when the skin is exposed to a vibration source. This specific type can show a familial trait. It is confirmed by showing a response after use of a vortex mixer (a piece of lab equipment that mixes solutions in tubes).

 

References:

Jonathan A. Bernstein, et al. The diagnosis and management of acute and chronic urticaria: 2014 update. J Allergy Clin Immunol Volume 133, Number 5.

Usmani N,Wilkinson SM. Allergic skin disease: investigation of both immediate and delayed-type hypersensitivity is essential. Clin Exp Allergy 2007;37:1541-6.

Zuberbier T, Maurer M. Urticaria: current opinions about etiology, diagnosis and therapy. Acta Derm Venereol 2007;87:196-205.

Chronic urticaria and angioedema: Part 1

Urticaria is the medical term for what we commonly call hives. It is often caused by an allergic process, but can occur for other reasons. Angioedema is swelling affecting the dermis, subcutaneous tissue, mucosa and submucosal tissues. Angioedema can be dangerous, particularly when the airway is obstructed by swelling.

Notably, the two conditions are closely related and are distinguished by the tissues affected. Urticaria is affects only the upper dermis. In this way, angioedema is sometimes considered a form of “inside hives”. These symptoms can occur as a result of allergy but also occur for other reasons.

Urticaria and angioedema are considered acute if they last for less than six weeks and chronic if they last for six weeks or more. Acute urticaria and angioedema are most often, but not always, the result of mast cell and basophil activation by both IgE and non-IgE mechanisms. Activation by complement fragments, antibody binding complexes, cytokines and blood pressure changes can contribute. Importantly, acute urticaria and angioedema usually have an obvious trigger and resolve on their own. Antihistamines and brief courses of steroids are generally used to manage symptoms.

Chronic urticaria usually does not an identifiable cause. The duration of CU (chronic urticaria and angioedema) varies, but physical urticarias are more likely to be long lasting. It is thought that CU affects 0.5-5% of the population. CU patients can have urticaria and angioedema, either alone or together. In these patients, cutaneous mast cells are the driving force and histamine is the most important mediator in these processes.

When biopsied, CU lesions often reveal infiltrates of lymphocytes, but sometimes other cells are present in infiltrates. In CU patients, the clotting cascade is sometimes activated, resulting in increased prothrombin fragments F1 and 2, and D-dimer. These have been suggested as markers of CU, but have not been verified.

CU is only rarely an IgE mediated reaction and is instead associated with a number of chronic conditions. Chronic infections like hepatitis B and C, EBV, HSV, helminthic parasites and H. pylori have been found to cause CU. Complement deficiencies, cryoglobulinemia, serum sickness, connective tissue disease, lupus, rheumatoid arthritis, thyroid disease (both hypo- and hyper-), neoplasms (such as SM), endocrine disorders and use of oral contraceptives are all linked to CU.

Autoimmune diseases are so frequently associated with CU that these patients are subclassified as having autoantibody associated urticaria. Autoantibody associated urticaria and angioedema, linked to thyroid antibodies, anti-IgE antibodies and anti-IgE receptor antibodies, is a subset of chronic idiopathic urticaria. Lupus, dermatomyositis, polymyositis, Sjogren’s and Still’s disease are all associated with CU. Celiac disease has been linked as well.

30-50% of CU patients make IgG antibodies to the IgE receptor and 5-10% make IgG to the IgE molecule. This often does not correlate with skin tests with the patient’s own serum or plasma (ASST, APST) and these tests are not known to affect treatment or identify a specific subgroup of patients. The importance of these IgG antibodies is not clear. Some consider these patients to be more severe, but it is not yet fully understood.

 

References:

Jonathan A. Bernstein, et al. The diagnosis and management of acute and chronic urticaria: 2014 update. J Allergy Clin Immunol Volume 133, Number 5.

Usmani N,Wilkinson SM. Allergic skin disease: investigation of both immediate and delayed-type hypersensitivity is essential. Clin Exp Allergy 2007;37:1541-6.

Zuberbier T, Maurer M. Urticaria: current opinions about etiology, diagnosis and therapy. Acta Derm Venereol 2007;87:196-205.

The comedown

Last fall, I talked with my doctors about removing my rectum. I have had colitis for years.  It hurts and bleeds all the time.

In January, my surgeon scheduled surgery to remove it. This would eliminate all possibility of reversing my ostomy. I was fine with that.

In February, my GI specialist told me I could get a subtotal colectomy and reverse the ostomy.

A week later, my surgeon told me he thought it might be better to just remove the entire colon.

Last Thursday was the two year anniversary of placing my colostomy. My surgeon called me that night to tell me that he had run into my GI specialist and they had together decided to reverse the ostomy and not remove all of the colon because if they are wrong “they can’t put it back”. This removes some colon but for complicated reasons I’m too frustrated to explain right now, there is a rock solid chance that I will end up exactly where I was two years ago before I got my ostomy. A place I swore I would never be again. He offered that if it didn’t work, then we would remove the rest in another surgery.

My hospital time after placing my colostomy is pretty hazy. I remember waking up in the recovery room and pulling the blanket, straining my neck to see the stoma. A nurse ran over and pulled the blanket up; she didn’t want me to see it until my surgeon was there. I watched her walk away before I looked again. It protruded about an inch, was pink and puckered, easily visible through the clear ostomy bag. “Like a rosebud,” my surgeon said. Yes, exactly like that.

The first time I stooled with it was a wonder, this painless relief. It didn’t last, but it was wonderful while it lasted. It hurt, but not as bad as my rectum had hurt before. Not as bad as the agony of not being to go to the bathroom, of constant distension, of your insides wrenching to no effect. No, not that bad, not like that.

I chose to get a colostomy. It’s not a choice that all colostomates get; some people suffer a terrible injury and wake up to a bag around a surgical opening into their intestines. I chose to get a colostomy, and I live with that choice every day, and every day I would say to myself, having this is a good thing. I believed it most days, if only to avoid arguing with myself. It is an act of self preservation, this sort of aggressive acceptance of your body.

Right up until the second my doctor told me he felt I could reverse the ostomy, I had never even considered it. How could I have, when before was so bad? No, I never did. This was part of my choice; I understood when I got it that it would be forever.

Right up until the second my doctor told me he felt I could reverse the ostomy, I never wanted to reverse it. But as soon as he said it, I did. I wanted it more than anything I’ve wanted in a long time.

Now I am looking at the very real possibility of ending up in the position of eventually not being able to stool again without serious intervention. At the very least, not without another surgery in the future. And that’s really stupid, it’s really stupid to decide to do this, because I’m so literally tired of surgery and procedures and shots and IV meds and this fucking port and its stupid dressing and I’m so literally tired of being sick right now that all I want is to not do this anymore. I don’t want to do this anymore. Because I have four feet of trigger living inside of my body and now I’ll never be able to stop cleaning up puke from my toilet every day and reacting to the smell of alcohol when I hook up IV fluids every night and taking the mountains of pills I push around every morning in the pillbox with a resigned finger. I am allergic to my own body and how can I ever get better when I’m literally allergic to myself?

I just want to get better and I’m never going to. But I still want it, I want it more than anything and knowing that I’m never going to doesn’t make me want it any less.

Two years ago, I woke up and saw my stoma, and for many days after that, I told myself it was a good thing, if only to avoid arguing with myself.

Four months ago, I was fine with having an ostomy forever and now I’m getting rid of it and I wish they had never told me I could.

All these plans I have made seem farcical now because they depend on me not reacting to being in pain all the time and that is only possible if I’m not in pain all the time.

Dreams are great and all, but the comedown when they are smashed is fucking hell.

Prostaglandin E2, mast cells and asthma

In the mast cell community, we talk about prostaglandins a lot. Most of the time we are talking about prostaglandin D2, as it is well produced by mast cells. However, there are a number of other prostaglandins that can affect inflammation and disease processes.

Prostaglandin E2 has been inflammatory and anti-inflammatory effects in the body. It is the prostaglandin responsible for inducing fevers. It is also a vasodilator, which contributes in some models to swelling. It relaxes smooth muscle and interferes with release of norepinephrine. PGE2 can cause hyperalgesia, or exaggerated pain response, a hallmark of inflammation. It regulates blood pressure, body temperature, sleep-wake pattern, kidney function and peristalsis (movement through the GI tract), and intestinal secretion.

It activates T cells and favors development of certain types of T cells that participate in the allergic response. It also modulates B cell activity and allergic reactions. However, it makes other immune cells less active. PGE2 simulates bone resorption and is important in reproduction, softening the cervix and causing uterine contractions.

PGE2 has a number of interactions with mast cells. In mast cells from bone marrow or peritoneal cavity, it induces histamine, IL-6 and GM-CSF release. However, in mast cells from progenitor cells or in the lung, it decreases release of leukotrienes, TNF and histamine. PGE2 acts on mast cells to reduce expression of PGE receptors, EP2 and EP3. PGE2 can enhance IgE production by B cells but also interferes directly with mast cell degranulation stimulated by IgE.

Prostaglandin E2 has a very unusual relationship with allergic inflammation. In contrast to prostaglandin D2, which constricts the airway, PGE2 actually relaxes the smooth muscle and opens the airway. Importantly, PGE2 retains this ability regardless of the trigger for reactive airway – allergen, asthma or exercise. Curiously, it was observed early on to cause coughing.

An interesting fact is that administration of medications that interfere with COX-2 (like Celebrex or aspirin) can worsen airway function and increase inflammation. This is of particular note in asthma patients. It is thought that this may be due to reducing production of PGE2.

 

References:

Emanuela Ricciotti, Garret A. FitzGerald. Prostaglandins and Inflammation. Arterioscler Thromb Vasc Biol. 2011; 31: 986-1000.

Rosa Torres, César Picado, Fernando de Mora. The PGE2–EP2–mast cell axis: An antiasthma mechanism. Molecular Immunology 63 (2015) 61–68

Daniel F. Legler, Markus Bruckner, Edith Uetz-von Allmen, Petra Krause. Prostaglandin E2 at new glance: Novel insights in functional diversity offer therapeutic chances. The International Journal of Biochemistry & Cell Biology 42 (2010) 198–201.

Mast cell mediators: Prostaglandin D2 (PGD2)

Prostaglandin D2 (PGD2) is the predominant prostaglandin product released by mast cells. It is found prevalently in the central nervous system and peripheral tissues, where it performs both inflammatory and normal processes. In the brain, PGD2 helps to regulate sleep and pain perception. PGD2 can be further broken down into other prostaglandins, including PGF2a; 9a, 11b-PGF2a (a different shape of PGF2a), and forms of PGJ. 9a, 11b-PGF2a shares the same biological functions as PGD2. Both of these can be tested for in 24 hour urine test as markers of mast cell disease.

PGD2 is a strong bronchoconstrictor. It is 10.2x more potent in this capacity than histamine and 3.5x more potent than PGF2a. It has been associated with inflammatory and atopic conditions for many years. Presence of allergen activates PGD2 production in sensitized people. In asthmatics, bronchial samples can achieve over 150x the level of PGD2 compared to controls. Elevated PGD2 has been associated with chronic coughing.

PGD2 is a driver of inflammation in many settings. It acts on bronchial epithelium to cause production of chemokines and cytokines. It also brings lymphocytes and eosinophils to the airway, which induces airway inflammation and hyperreactivity in asthmatics. PGD2 may also inhibit eosinophil cell death, resulting in further inflammation.

An interesting facet of PGD2 is its role in nerve pain. It has been found that PGD2 is produced by microglia in the spine after a peripheral nerve injury. These cells make more COX-1, which then makes PGD2. Newer COX-2 inhibiting NSAIDs do not affect nerve pain in mouse models, but older NSAIDs that inhibit COX-1 and COX-2 reduce neuropathy.

PGD2 is found to inhibit inflammation in other settings. It can reduce eosinophilia in allergic inflammation in mouse models. Additionally, once the acute phase of inflammation is over and it is resolving, administering a COX-2 inhibitor actually makes the inflammation worse. This indicates that PGD2 may be important in resolving inflammation in some processes.

Aspirin is commonly used in mast cell patients to inhibit prostaglandin production. PGD2 is primarily manufactured by COX-2, but the pathway that evokes neuropathy uses COX-1. There are a number of COX-1 and COX-2 inhibitors available.

In mast cell patients, PGD2 is probably most well known for causing flushing. This happens due to dilation of blood vessels in the skin. Due to a well characterized response to aspirin, this is generally the first line medication choice. Some salicylate sensitive mast cell patients undergo aspirin desensitization to be able to use this medication.

 

References:

Emanuela Ricciotti, Garret A. FitzGerald. Prostaglandins and Inflammation. Arterioscler Thromb Vasc Biol. 2011; 31: 986-1000.

Matsuoka T, Hirata M, Tanaka H, Takahashi Y, Murata T, Kabashima K, Sugimoto Y, Kobayashi T, Ushikubi F, Aze Y, Eguchi N, Urade Y, Yoshida N, Kimura K, Mizoguchi A, Honda Y, Nagai H, Narumiya S. Prostaglandin D2 as a mediator of allergic asthma. Science. 2000;287: 2013–2017.

G Bochenek, E Nizankowska, A Gielicz, M Swierczynska, A Szczeklik. Plasma 9a,11b-PGF2, a PGD2 metabolite, as a sensitive marker of mast cell activation by allergen in bronchial asthma. Thorax 2004; 59: 459–464.

Victor Dishy, MD, Fang Liu, PhD, David L. Ebel, BS, RPh, George J. Atiee, MD, Jane Royalty, MD, Sandra Reilley, MD, John F. Paolini, MD, PhD, John A. Wagner, MD, PhD, and Eseng Lai, MD, PhD. Effects of Aspirin When Added to the Prostaglandin D2 Receptor Antagonist Laropiprant on Niacin-Induced Flushing Symptoms. Journal of Clinical Pharmacology, 2009; 49: 416-422

Prostaglandins and leukotrienes

Prostaglandins are molecules that behave like hormones and are used for signaling between cells. They are produced by many cell types and tissues in the body.

To make prostaglandins, an enzyme called phospholipase A2 turns diacylglycerol into arachidonic acid (AA). All prostaglandins are derived from AA and this molecule is mentioned often in scientific literature about mast cells, as it is easier to detect AA than some prostaglandins. Once AA has been produced, one of two things happen: AA is either changed by the cyclooxygenase (COX) pathway into prostaglandins and thromboxanes or by the lipoxygenase (LO) pathway into leukotrienes.

Prostaglandins, thromboxanes and leukotrienes are all types of eicosanoids. Eicosanoid is another common word in mast cell literature, and in that context it usually refers to prostaglandins or leukotrienes.

To make prostaglandins from AA, cells use the enzymes COX-1 and COX-2. COX-1 produces regular low levels of prostaglandins, whereas COX-2 makes prostaglandins in response to inflammation. Other enzymes called prostaglandin synthases finish off making the prostaglandins into the right shapes. To make leukotrienes from AA, cells use the enzyme arachidonate 5-lipoxygenase.

There are a number of medications that interfere with the production of leukotrienes or prostaglandins by interfering with the enzymes that make them. This is generally regarded as a more effective way to treat symptoms from these products, rather than trying to block their action after they have been made.

Non steroidal anti-inflammatories (NSAIDs), of which there are dozens, interfere with the activity of both COX-1 and COX-2. Newer COX-2 inhibitors like Celebrex only inhibit COX-2. Vitamin D downregulates expression of COX-2. A chemical in St. John’s Wort is also a COX-1 inhibitor. Zileuton is a lipoxygenase inhibitor.

Mast cell medications: Everything but antihistamines

The following medications listed are available in oral, intramuscular or intravenous formulation. Not all medications are available in the US or Europe. Topical and inhaled medications are not included in these lists.

Mast cell stabilizers interfere structures on the cell membrane required for degranulation and thus prevent the release of granule contents, including histamine.

Mast cell stabilizers
Cromolyn sodium/ Cromoglicic acid/ Nedocromil
Ketotifen
Omalizumab*
Quercetin
*mechanism unclear

 

Beta-2 adrenergic agonists cause smooth muscles to relax, which allow airways to open. These are used almost exclusively in asthma and pulmonary disease, which a secondary use in controlling uterine contractions in labor.

Beta-2 adrenergic agonists
Albuterol
Terbutaline

 

Leukotriene receptor antagonists work by interfering with the function of leukotrienes by blocking the CysLT1 receptor. Leukotrienes are heavily involved in airway reactivity and inflammation.

Leukotriene receptor antagonists
Montelukast
Pranlukast
Zafirlukast

 

5-lipoxygenase inhibitors prevent leukotrienes from being made.

5-lipoxygenase inhibitor
Curcumin
St. John’s Wort
Zileuton

 

Corticosteroids interfere with the activity of mast cells and production of mast cell mediators.

Mast cell stabilizers
Budesonide*
Dexamethasone
Hydrocortisone
Prednisone
Prednisolone
*taken orally, with effects local to the GI tract

 

Proton pump inhibitors reduce the production of gastric acid and treat heartburn, nausea and reflux. This can also be achieved by H2 antihistamines and for this reason, the two classes are often confused. The following medications, which are taken often by mast cell patients, have no known antihistamine effect. They can safely be taken with H2 antihistamines and help many mast cell patients, but it is important to clarify that they are NOT antihistamines.

Proton pump inhibitors
Dexlansoprazole
Esomeprazole
Ilaprazole
Lansoprazole
Omeprazole
Pantoprazole
Rabeprazole

Mast cell medications: Antihistamines by receptor activity

The following medications listed are available in oral or intravenous formulation. Not all medications are available in the US or Europe. Topical and inhaled medications are not included in these lists.

H1 antihistamines interfere with the action of histamine at the H1 receptor. This can help with many symptoms, including flushing, itching, hives, burning skin, nasal congestion, sneezing, constriction of airway, shortness of breath, GI cramping, diarrhea, gas, abdominal pain, tachycardia, blood pressure variability or dizziness. What symptoms are best alleviated varies with the medication; they do not all address all symptoms equally.

First generation Second and third generation Atypical antipsychotics
Alimemazine Acrivastine Aripiprazole
Azatadine Astemizole Asenapine
Benztropine Azelastine Clozapine
Bepotastine Bepotastine Iloperidone
Brompheniramine Bilastine Olanzapine
Buclizine Cetirizine Paliperidone
Captodiame Clemastine Quetiapine
Carbinoxamine Clemizole Risperdone
Chlorcyclizine Clobenztropine Ziprasidone
Chloropyramine Desloratadine Zotepine
Chlorpheniramine Ebastine
Chlorphenoxamine Emedastine
Cinnarizine Epinastine Typical antipsychotics
Clemastine Fexofenadine Chlorpromazine
Cyclizine Ketotifen Flupenthixol
Cyproheptadine Latrepirdine Fluphenazine
Dexbrompheniramine Levocabastine Perphenazine
Dexchlorpheniramine Levocetirizine Prochlorperazine
Dimenhydrinate Loratadine Thioridazine
Diphenhydramine Mebhydrolin Thiothixene
Diphenylpyraline Mizolastine
Doxylamine Rupatadine
Embramine Setastine Tetracyclic antidepressants
Etodroxizine Talastine Amoxapine
Ethylbenztropine Terfenadine Loxapine
Etymemazine Maprotiline
Flunarizine Mianserin
Histapyrrodine Tricyclic antidepressants Mirtazapine
Homochlorcyclizine Amitriptyline Oxaprotiline
Hydroxyethylpromethazine Butriptyline
Hydroxyzine Clomipramine
Isopromethazine Desipramine
Meclizine Dosulepin
Mequitazine Doxepin
Methdilazine Imipramine
Moxastine Iprindole
Orphenadrine Lofepramine
Oxatomide Nortriptyline
Oxomemazine Proptriptyline
Phenindamine Trimipramine
Pheniramine
Phenyltoloxamine
Pimethixene
Prometheazine
Propiomazine
Talastine
Thonzylamine
Tolpropamine
Tripelennamine
Triprolidine

 

H2 antihistamines interfere with the action of histamine at the H2 receptor. This helps mostly with symptoms affecting the GI tract, such as abdominal pain, nausea, and diarrhea. To a lesser extent, H2 antihistamines can decrease vasodilation.

H2 antagonists
Cimetidine
Famotidine
Lafutidine
Nizatidine
Ranitidine
Roxatidine

 

There are few H3 antihistamines and for this reason, their exact effects are largely unknown.  However, in research, H3 antihistamines modulate nerve pain and may normalize the release of several neurotransmitters, including serotonin.

The only medication with known H3 activity available for patient use as an antihistamine anywhere in the world is betahistine. It is anti-vertigo drug used mostly in treatment of Meniere’s disease and other balance disorders. Betahistine actually increases release of histamine and for this reason has been associated with the risk of severe allergic events while taking it.

A 2014 paper described for the first time the H3 reverse agonist/ selective antagonist effects of two antiarrhythmic drugs, amiodarone and lorcainide. This is a very new finding and has not been investigated yet in humans; however, this behavior would explain some of the neurologic effects of these two medications.

H3 antihistamines
Amiodarone*
Betahistine
Lorcainide*

 

Thioperamide has shown promise in research as an H3 and H4 antihistamine, but is not available for patient use.

I have seen blurbs on forums and the internet in which people state that amphetamines are H3 antagonists and doxepin is an H4 antihistamine. I cannot find any evidence that this is the case. Amphetamines interact with the transport of histamine in a very complex way, and that can theoretically interfere with the ability of cells to use histamine. However, this is not the same as a true antihistamine, and the effect of amphetamines on histamine has been difficult to quantify.

Mast cells in vascular disease: Part 2

Chymase is a mediator produced and released by mast cells. It is an enzyme that converts angiotensin I to angiotensin II, which is important in regulating blood pressure. Chymase can also activate TGF-b1, IL-1b and degrade some of the proteins that hold cells together in tissues.

Release of chymase by local mast cells is a large factor in plaque instability. This is thought to be by raising amount of angiotensin II and degrading a structure that stabilizes the plaque. Chymase also causes apoptosis, or cell death, of smooth muscle cells, which lie underneath the plaque. It was recently discovered that activation of the toll like receptor 4 (TLR4) on the surface of the mast cell causes the mast cell to release IL-6. IL-6 then binds to the mast cell and causes it to make and release chymase.

Chymase and tryptase also interfere with cholesterol transport. In plaques, macrophages eat cholesterol and become foam cells. When the foam cells try to release the cholesterol, chymase and tryptase can prevent this, which stabilizes the plaque and makes it larger.

Mast cell activation is also known to affect plaque behavior. In mast cells that could not be activated by IgE, the size of the plaque and cell death around it were reduced. IgE levels are higher in patients who suffer acute coronary syndromes compared with those who don’t, with IgE levels peaking seven days after the event. Patients with hyper-IgE syndrome are much more likely to have coronary artery dilation or aneurysm, although atherosclerosis was not common. A whole body MRI detected impaired vascular integrity in these patients. These patients are expected to be more prone to mast cell activation.

In mastocytosis patients, no increase in atherosclerosis has been reported, though cardiovascular symptoms are not unusual. Some mastocytosis patients demonstrate vascular instability. Two cases of strokes due to cranial artery dissection have been published.

Mice that lack substance P, a neuropeptide that activates mast cells, have better cardiac function than expected. In mouse models, adding substance P to a plaque could cause hemorrhage only if the mouse had mast cells. This indicates that mast cell activation is important in plaque rupture.

 

References:

Simon Kennedy, Junxi Wu, Roger M. Wadsworth, Catherine E. Lawrence, Pasquale Maffia. Mast cells and vascular diseases. Pharmacology & Therapeutics 138 (2013) 53–65.

Ramalho, L. S., Oliveira, L. F., Cavellani, C. L., Ferraz, M. L., de Oliveira, F. A., Miranda Corrêa, R. R., et al. (2012). Role of mast cell chymase and tryptase in the progression of atherosclerosis: study in 44 autopsied cases. Ann Diagn Pathol 17, 28–31.

Meléndez, G. C., Li, J., Law, B. A., Janicki, J. S., Supowit, S. C., & Levick, S. P. (2011). Substance P induces adverse myocardial remodelling via a mechanism involving cardiac mast cells. Cardiovasc Res 92, 420–429.

Guo, T., Chen,W. Q., Zhang, C., Zhao, Y. X., & Zhang, Y. (2009). Chymase activity is closely related with plaque vulnerability in a hamster model of atherosclerosis. Atherosclerosis 207, 59–67.

 

What do all these words mean? (Part 2)

What does it mean if a person is CD117 positive in a biopsy? Is this bad?

In the context of mast cell disease, it usually just means that mast cells were found.

 

If CD117 is normal for mast cells, why are people sometimes “negative for CD117” on biopsies?

This sometimes happens. When you have mast cell disease, you often have more CD117 receptors on mast cells. This makes it easier for the test to find them. So when you are found to be “negative for CD117” in regards to mast cell disease, you are not truly “negative”. You just express a lower amount of CD117 receptors so the test didn’t see them.

 

I am a mast cell patient and my bone marrow biopsy was positive for CD117. How do I know that it is normal mast cells that show CD117 and not these other dangerous cells you mentioned?

You can tell by looking at the cells with special stains. Pathologists and immunohistochemistry scientists are very skilled at distinguishing one cell type from another. They can tell based upon what the cell looks like in addition to being positive for CD117.

 

If I am CD117 positive in a biopsy, does that mean I am “CKIT positive”?

No. If I could do away with one single phrase in mast cell terminology, it would be CKIT+.

CKIT+ is a term used to mean “positive for the D816V mutation in codon 816 of the CKIT gene”. It means you are positive for a mutation that has been associated with neoplastic disorders of mast cells. So when people say they are CKIT+, they mean they were found to have a mutation. They do NOT mean they were found to have CKIT/CD117 on their mast cell surfaces, because this is totally normal and is the case for everyone.

Additionally, the test to detect CD117 on a cell surface is NOT the same test used to identify the D816V mutation. That test breaks open the cells and looks for a specific mutation in the DNA sequence. They are not run at the same time.

 

Why is it important to know if I am positive for the D816V mutation (CKIT+)?

The D816V mutation changes the shape of the CKIT receptor. Due to this wrong shape, the receptor does not need SCF to bind to the receptor to tell the mast cell to live longer. In this new shape, the receptor is stuck in an “activated” position, so it is telling the cell to live longer all the time, without SCF. This is called “autoactivation”.

The D816V mutation is one of the minor criteria for systemic mastocytosis, so it is important for classification purposes. Also, it may affect your treatment plan in the unlikely situation of needing chemotherapy.

 

What is CD25?

CD25 is part of a receptor for a molecule called IL-2. Normally, mast cells do not express receptors for IL-2, which is a molecule that regulates development of T cells. When mast cells express CD25, it is an indication that the mast cell is neoplastic. Many T cells normally express CD25, so if it is on a biopsy report, keep in mind that it’s abnormal on mast cells, but not everywhere.

Presence of CD25 on mast cells is one of the minor criteria for SM.

 

What is CD2?

CD2 is an example of a “CD” molecule that is not a receptor. It is a cell adhesion molecule so it helps cells stick together. Normally, mast cells do not express CD2. When mast cells express CD2, it is an indication that the mast cell is neoplastic. Many T cells normally express CD25, so if it is on a biopsy report, keep in mind that it’s abnormal on mast cells, but not everywhere. CD2 is a less accurate indication of SM than CD25.

Presence of CD2 on mast cells is one of the minor criteria for SM.

 

What is CD30?

CD30 is a receptor for proteins associated with tumor necrosis factor. It is commonly referred to as a tumor marker, but this is not always the case. CD30 has recently been shown to be frequently positive in patients with all forms of SM (ISM, SSM, SM-AHNMD, ASM). However, on other cells besides mast cells, it may indicate lymphoma or other conditions.

 

What is CD34?

CD34 is another cell adhesion molecule. It is thought to allow stem cells to attach to proteins in the bone marrow. It is found on many progenitor cells, cells that later become other kinds of cells. Mast cells express CD34, though this tends to be lost as they move into tissues.