This morning’s NEJM case was a patient with systemic mastocytosis. Here’s the learning points from the case.
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- Diarrhea that fails to abate with fasting suggests a secretory cause. Nocturnal diarrhea almost always has an organic cause.
- Systemic illnesses are rarely the cause of flushing, but they should be suspected in the presence of suggestive symptoms and signs, such as urticaria pigmentosa (mastocytosis) or hypotension and diarrhea (carcinoid syndrome).
- Symptomatic treatments for systemic mastocytosis include H1- and H2-antihistamines, cromolyn sodium, and leukotriene-receptor inhibitors. Treatments for specific complications include calcium, vitamin D, and bisphosphonates for osteoporosis; antimotility agents for diarrhea; epinephrine for anaphylaxis; and proton-pump inhibitors for acid hypersecretion.
- Treatments to reduce mast-cell burden in systemic mastocytosis include interferon alfa and cladribine.
- Systemic mastocytosis is a clonal disorder of stem cells, usually associated with the KIT D816V activating mutation of the stem-cell-factor receptor gene. In most instances it is not responsive to the tyrosine kinase inhibitor imatinib. Experimental therapies include novel tyrosine kinase inhibitors.
- Serum tryptase levels are the most useful screening test in patients with suspected systemic mastocytosis.