A 6-month old with total body flushing and a macular-papular lesion.

Flushing of the skin of an infant may be a sign of the child's first allergic reaction to food, insect envenomation, or other allergens, a sign of sepsis, or due to dilation of cutaneous vessels caused by a vasodilator substance or neural mechanisms. A rare cause of this condition results in the release of mast cell mediators such as histamine, prostaglandin D2, tryptase, chymase, and leukotrienes. We present a case of a 6-month-old with severe total body flushing and a yellow-tan, raised, well-demarcated lesion on the thigh consistent with a solitary mastocytoma. Erythema was most pronounced adjacent to the lesion, suggesting a positive Darier sign. Subsequent evaluation by a dermatologist confirmed the diagnosis, and the patient underwent no further therapy; however, the family was appropriately counseled on management if the symptoms were to reappear. Appropriate diagnosis and management of this patient and other forms of mastocytosis in children are discussed.