(BMJ)—A boy 6 months of age presented with flushing episodes associated with facial swelling and agitation. A red lesion on his R leg, present since birth, became inflamed and fluid filled during these episodes. Exam: 3x1-cm tanned, red lesion on R leg. What's the dx?
Lymphomatoid papulosis
Mastocytoma
Cutaneous pseudolymphoma
Carcinoid
Juvenile xanthogranuloma
You are correct. Mastocytoma is a cutaneous mast cell lesion that causes local itching and blistering and occasionally presents with systemic sx caused by release of mast cell mediators. Triggers include localized irritation. Mastocytomas are benign and typically resolve during childhood. Referral to dermatology is recommended for dx.

BMJ 2016;353:i2763
By vgreene, 9 September, 2016

AAP