Mast Cell Activation Syndrome - Twitter summary from 2014 #ACAAI meeting

Excerpts from Meet the Professor small group session titled "Mast Cell Activation Syndrome", led by Fred Hsieh and Mariana Castels.

In reality, the talk included both clonal mast cell disease (aka systemic mastocytosis or SM) and non-clonal (mast cell activation MCAS).

Systemic mastocytosis (SM) has major and minor criteria for diagnosis and staging for treatment.

SM diagnosis is confirmed if there is one major AND one minor, or three minor criteria are fulfilled. SM major criteria include mast cell aggregates of 15 mc/hpf not in skin (bone marrow, liver, etc), confirmed by positive tryptase. SM minor criteria include serum tryptase higher than 20 ng/ml, mast cells with CD117 CD2 and/or CD25, c-KIT mutation, more than 25% atypical MC in biopsy.

Non-clonal Mast Cell Activation Syndrome (nc-MCAS) is like clonal but with no aggregates plus c-KIT and CD25 in BM, tryptase may be high. It's confusing, but Non-clonal MCAS is also called Monoclonal MCAS or ncMCAS = MMCAS. Presentation can be very similar between SM and MMCAS. A nice reference for MCAS by Cem Akin is available online at JACI

Symptoms include flushing, palpitations, presyncope, headache, SOB, N/V/diarrhea, abdominal pain, fatigue/brain fog, rashes, low BP, etc.

MCAS triggers include idiopathic, hymenoptera venoms, EtOH, emotional stress, physical stressors (heat, cold, temp changes, vibration, friction of skin lesions), exercise, latex, odors/perfumes, medications, histamine-containing foods.

Medication triggers of MCAS include morphine and derivatives, IV vanco, NSAIDS, anesthesia (sux, tubocurarine, gallamine), radiocontrast dye. Exercise can also be a trigger, making MCAS difficult to distinguish from exercise-induced anaphylaxis.

We learned, err were reminded, from FIT Bowl last night that the uterus has the second most of mast cells behind the skin. But infertility is not usually associated with mast cell activation syndromes.

Histamine-rich or releasing foods can be problematic in patients with MCAS. Here's a nice list-

Fentanyl is the best opiate for pain in mastocytosis patients although it should be administered with extreme caution.

Skin manifestations of MCAS: hives, flushing, urticaria pigmentosa (pathognomonic), telangiectasia (TMEP), solitary mastocytoma, diffuse cutaneous mastocytosis.

Urticaria pigmentosa consists of reddish-brown hives that swell with friction (Darier's sign) In kids, 85% of urticaria pigmentosa will resolve by puberty, but we still need to follow tryptase, CBC and LFTs to monitor.

Hymenoptera stings can unmask indolent MCAS, and tryptase should be considered part of workup for sting hypersensitivity, especially with negative skin tests. For MCAS patients with hymenoptera hypersensitivity, Dr Castells still does venom IT, and even ultra-rush IT, although buildup can be tough. There is a paper on using omalizumab for difficulty in escalating dose of venom IT Dr Castells recommends venom IT for LIFE in hymenoptera sensitive MCAS patients. They should also have three (3) Epipens at all times.

Mast cell biomarkers for targeted therapy in MCAS and related conditions include: tryptase,c-kit D816V, urinary methylhistamine, urinary prostaglandin D2, urinary prostaglandin F-alpha (the test is available only at Mayo). For 24 hr urinary histamine and prostaglandins, Dr Castells requires positive tests on TWO separate occasions. Mediators are important for targeted therapy. If PGs are only positive, the patient might be a candidate for aspirin therapy.

Interestingly, tryptase is not a particularly good marker for food-induced anaphylaxis, like other reactions (drugs) or MCAS. Mast cell carboxypeptidase may be a better marker for food anaphylaxis. But any time a patient has two organ systems involved with anaphylaxis, you will often see an elevated serum tryptase.

The majority of kids with normal tryptase and UP are generally not “bone marrow’d” and just symptomatically treated, given good prognosis. But we need to check CBC/LFT/tryptase. If these are grossly abnormal or if patients have severe GI symptoms, then you should do a bone marrow biopsy. Regarding bone marrow biopsy, it is important to have a pathologist who is familiar with identifying MCAS on bone marrow biopsy.

Guide treatment based on markers. Useful medications include H1 and H2 antihistamines, oral cromolyn (gastrocrom), ketotifen, leukotriene inhibitors, steroids, anti-IgE.

A large portion (Dr Castells estimates 50%) of idiopathic anaphylaxis may be some form of MCAS.

A great resource for MCAS is the Mastocytosis Society (@tmsforacure)

This is a Twitter summary from 2014 #ACAAI meeting. The post is a part of series. See the rest here:

The Twitter summary was made possible by @DrAnneEllis and @MatthewBowdish

Several allergists did a great job posting updates from the 2014 meeting of the #ACAAI. I used the website “All My Tweets” to review the tweets. For comparison, here are the tweets from previous #ACAAI meetings (scroll down the page for the past years):

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