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Intertriginous cutaneous mastocytosis in a 16‐year‐old boy

boy Editor, Mastocytosis is a disease characterized by the proliferation of mast cells in several organs, including the skin, bone marrow, liver, spleen, and gastrointestinal tract. The eruption can have multiple clinical presentations but usually appears as red–brown macules or papules with severe pruritus. However, intertriginous persistent yet asymptomatic papular lesions are rare. A 16-year-old male patient presented with lesions in the intertriginous regions that had developed slowly with no symptoms over 10 years. Clinical examination revealed symmetrically distributed, small, brown, flat papules and maculopapules in the axillae (Fig. 1) and groin without scaling. Darier's sign was negative in the affected sites. A general physical examination was otherwise normal. The subject denied having pruritus, diarrhea, abdominal pain, headache, anaphylaxis, and bone pain. His family history was negative for any similar disorder. A skin biopsy taken from one of the brown papules in the left axilla showed enlarged dermal papillas infiltrated mainly by dense spindle-shaped cells with oval to fusiform nuclei and scantly eosinophilic cytoplasm. Similar cells were found around the vessels in the upper dermis (Fig. 2). Both toluidine blue and CD117 stain results were positive (Figs. 3 and 4). Routine examination and bone marrow aspiration were advised but rejected by the patient's parents. Considering the clinical appearance and histopathological results, our final diagnosis was intertriginous cutaneous mastocytosis. As the lesions were asymptomatic and were not progressing at a significant rate, no treatment was prescribed. The patient remains under follow-up. Cutaneous mastocytosis is a rare disorder, which normally presents as symmetrically distributed red–brown macules or papules that develop wheals, erythema, and