What workup is needed for a patient with mastocytosis diagnosed through biopsy? The rash, which covers his arms and trunk and has begun to spread to his lower back and upper legs, itches when he takes a hot shower. The patient is a smoker, drinks one or two beers a day, and is on no medications.—SHELLY PALMER, PA-C, Lakefield, Minn.

The World Health Organization has established diagnositic criteria for mastocytosis. Cutaneous mastocytosis has skin lesions with typical clinical signs (i.e., urticaria pigmentosa, diffuse cutaneous mastocytosis, and telangiectasia macularis eruptive perstans) and the presence of at least one of the following in a skin lesion: (1) focal dense infiltrates (>15 mast cells per cluster) or diffuse mastocytosis infiltrates (>20 cells per high-power field) or (2) c-KIT D816V mutation. Systemic mastocytosis requires the presence of at least one major and one minor criterion or three minor criteria in the bone marrow or other extracutaneous organ. The major criterion is multifocal dense infiltrates of mast cells (>15 mast cells in aggregates). Minor criteria include: (1) mast cell infiltrates contain >25% spindle-shaped cells or other atypical morphologic features; (2) c-KIT D816 mutation; (3) expression of CD2 and/or CD25 on CD117-positive mast cells; and (4) serum tryptase levels >20 ng/ml (not valid if the patient has concomitant hematologic disorder). Recommended workup would initially include complete blood cell count, complete metabolic panel, and serum tryptase; subsequent studies would include a bone marrow biopsy and aspirate. If the diagnosis of systemic mastocytosis is confirmed, a staging evaluation (CT of chest, abdomen, and pelvis; bone scan and/or skeletal survey; and dual X-ray absorptiometry scan) would be appropriate. Additional information is available at Curr Opin Hematol. 2010;17:125-132, Ann Allergy Asthma Immunol. 2010;104:1-10, and Cutis. 2009;83:29-36.—Philip R. Cohen, MD (141-5)

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