This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Monoclonal mast cell activation syndrome (MMAS) is a rare immunological disorder characterized by recurrent episodes of allergy, flushing, stomach and intestinal cramping, diarrhea, wheezing, fatigue and a temporary loss of consciousness caused by a fall in blood pressure (hypotension). MMAS is very similar to systemic mastocytosis but without the itchy skin patches known as urticaria pigmentosa. Symptoms may be triggered by a number of factors, including eating, exertion, environmental conditions, emotional stress, or insect stings.[11133][11135] It is caused by a very small change (mutation) in the KIT gene which results in a defect of the mast cells. Treatment may include antihistamines and other medications, as needed.[11135]
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