Disseminated brown macules in an infant.

Urticaria pigmentosa is the most common form of mastocytosis. Mastocytosis usually presents at birth or early childhood, and may involve only the skin or, less commonly, other internal organs. Diagnosis is clinical, but a skin biopsy may be useful. Prognosis is usually good, and treatment focuses on the avoidance of certain triggers and administration of topical and systemic medications. Appropriate counselling of parents regarding the benign nature of this disease is important as most cases resolve by adolescence.