Abstract: A 5-month-old boy was noted to have brown macules with palpable infiltration on the head, trunk, and extremities a few weeks after birth, with recurrent episodes of generalized flushing and blistering in some of the macules. These lesions developed into yellowish plaques after 1 year of topical treatment with clobetasol propionate. Serum lipid levels were within normal limits. The appearance of the yellowish lesions was similar to that of the xanthelasmoid type of cutaneous mastocytosis. The brown macules showed infiltration of a large number of mast cells and a small number of scattered foam cells, whereas in the yellowish plaques, the number of foam cells was greatly increased. The yellowish plaques regressed spontaneously within a year after cessation of topical corticosteroid treatment. Immunohistochemical analysis found that the foam cells were stained with monocyte/macrophage markers including HAM56, and with SRA-C6, a monoclonal antibody to macrophage scavenger receptor class A (CD204). Therefore, the yellowish plaques were considered to be plane xanthoma associated with cutaneous mastocytoma.