Mastocytosis: one year's experience.

The diagnosis of systemic mastocytosis without urticaria pigmentosa has been made with increasing frequency since modern methods of histamine assay have been used clinically. We examined the incidence of urticaria-angioedema and mastocytosis over a recent 12-month period. Of 490 new patients we saw, 52 had urticaria-angioedema, and ten had evidence of excess histamine +/- PGD2, with at least ten mast cells per high-power field on skin biopsy. The average age was approximately 35 years; the male:female ratio was 1:4 for urticaria-angioedema and 1:2 for mastocytosis. Symptoms of mastocytosis included flushing, abdominal cramping/diarrhea, syncope, urticaria-angioedema, pruritus, and headache. Symptoms have typically been prevented by a combination of H1 and H2 antagonists, with addition of a cyclo-oxygenase inhibitor in syncopal cases. Acute hypotension has responded to epinephrine.