Cutaneous mastocytosis in an infant: Case report and clinicopathological correlation

Mastocytosis is a disorder of clonal proliferation of the mast cells, which can be cutaneous or systemic. Abnormal mast cell infiltration comprising multifocal compact clusters or cohesive aggregates can affect one or more organ systems. Cutaneous mastocytosis is a relatively uncommon condition in the pediatric population. We report a case of 9 month infant presented with multiple papular and vesicular skin rashes since 6 months of age. On clinical examination Darier’s sign was negative. The serum tryptase levels were within normal limits. Clinical differential diagnoses were benign cephalic histiocytosis vs cutaneous mastocytosis. Skin biopsy revealed a mononuclear cell infiltrate in the papillary dermis reaching up to the dermo-epidermal junction. Toluidine blue staining highlighted the metachromatic granules. CD117, CD30 IHC stains were positive which confirmed the diagnosis of cutaneous mastocytosis. This case is presented to highlight the histomorphology and the special stains in cases of mastocytosis.