Neonatal-onset maculopapular cutaneous mastocytosis presenting with pigmented plaques in an infant

Abstract

Cutaneous mastocytosis is a clonal disorder characterized by abnormal accumulation of mast cells in the skin. Maculopapular cutaneous mastocytosis (urticaria pigmentosa) is the most common form in children and usually presents within the first two years of life. Neonatal onset and blistering may complicate recognition and mimic other pigmentary dermatoses. We report a 10-month-old male with six well-defined brown plaques measuring 2–3 cm, two with central scars. A blister was noted at birth on the knee, followed by progressive lesion development. Physical examination revealed no lymphadenopathy or visceromegaly. Histopathology demonstrated dense dermal mast cell infiltration with metachromatic granules on Giemsa staining, confirming maculopapular cutaneous mastocytosis. The patient was treated with oral ketotifen with stable disease at six-month follow-up. Early recognition is essential to ensure appropriate counseling, monitoring, and avoidance of unnecessary investigations.