This summary was compiled from the tweets posted by allergists/immunologists who attended the 2013 annual meeting of the American Academy of Allergy Asthma and Immunology (AAAAI) (see the list at the end). The tweets were labeled #AAAAI. The text was edited and modified by me.Dr Todd Wilson presented an "Update in Mast Cell Biology and Mast Cell Disorders".
KIT and FcER1 are main signaling pathways on mast cells. Multiple genetic defects have been identified in the various phenotypes of mastocytosis. The more lineages involved, the worse prognosis.
The most common symptoms of mastocytosis are skin lesions, pruritus, flushing, diarrhea, and cramps, anaphylaxis, neuropsychiatric symptoms.
Mast cells. Image source: Wikipedia, public domain.
WHO Classification: cutaneous mastocytosis, systemic mastocytosis (5 subtypes), mast cell sarcoma, extra cutaneous.
Diagnosis: Look for activating mutations in KIT, must do a bone marrow biopsy. You can miss if only test blood. Mast cells are not in peripheral blood.
A study looked at patients with systemic reactions to Hymenoptera stings - 8% wer diagnosed with a clonal mast cell disorder.
Mast cell activation syndromes (MCAS)
MCAS is mast cell activation syndrome. The earliest discussion was in 1980s, a consensus conference looked at it in 1991. MCAS was defined in 2007.
MCAS diagnostic criteria include: 1. clinical symptoms, 2. increase in baseline serum tryptase by 20% + 2 NG/ml within 4 hours, 3. clinical symptoms response to antihistamines.
Mariana Castells, MD PhD presented on mast cell activation syndromes (MCAS).
The term MCAS covers a broad range of diseases, from acute anaphylaxis to systemic mastocytosis.
Majority of patients with mastocytosis have a mutation in c-kit. C-kit mutation can be determined from peripheral blood. Clonal mast cells express CD25. Mastocytosis due to D816V c-kit mutation is imatinib (Gleevec) resistant. Spindle-shaped mast cells satisfy minor criteria for mast cell disease.
Tryptase is under-utilized and poorly-understood test.
Mastocytosis work up: look for cutaneous lesions, full physical exam, labs (tryptase, LFTs, chem, CBC), bone marrow biopsy.
Mast cell activation syndrome can refer to patients with symptoms of mast cell mediator release, but without clonal disease. Mast cells in idiopathic MCAS appear normal, and do not aggregate. Patients with clonal mast cell disease experience recurrent episodes of hypotension, syncope or presyncope.
Mast cell diseases can be associated with mental “fogginess”, osteoporosis, severe reactions to drugs/venom. GI, cutaneous, and neurologic symptoms are common in idiopathic MCAS. Middle-aged women seem significantly affected. Is there a hormonal component?
Treatment
Indolent and smoldering systemic mastocytosis doesn't affect life span. Treat symptoms only - not with cytoreductive agents
Related:
Mast cell disorders/consensus report - Int Arch Allergy Immunol 2012;157:215-225.
Resources - TMS: The Mastocytosis Society website lists medical research centers. ECNM: European Competence Network on Mastocytosis.
Mast Cell Disorders - figures:
Allergists are on Twitter - follow them
Allergists increased Twitter use 470% in one year - 25 allergists reached 250,000 individuals from the 2012 #AAAAI meeting (see the references here). This summary was compiled from some of the tweets posted by the following allergists:
https://twitter.com/mrathkopf
https://twitter.com/allergistmommy
This is a list of the allergists who used Twitter to post updates from the 2013 #AAAAI meeting. The list is open for edit, please feel free to add your own info.
I would strongly encourage you to post updates on Twitter from the CME conferences that you are planning to attend in the future. Here is how to do it: Twitter for Physicians: How to use Twitter to keep track of the latest news and scientific meetings, and share information with colleagues and patients.
References:
Mast Cell Activation Disorders - 2014 free full text review http://buff.ly/1kPDdzo
Proposed diagnostic algorithm for patients with suspected mastocytosis. Allergy, 2014 http://buff.ly/1hZ4ayz
Disclaimer: The text was edited, modified, and added to by me. This is one of a series of posts that will be published during the next few weeks.