Last reviewed: October 2023
Author: Dr Stanley Leong, Dermatology and Paediatric Registrar, NZ.
Reviewing dermatologist: Dr Ian Coulson (2023).
Edited by the DermNet content department
A 3-year-old boy presented with multiple pigmented skin lesions on his trunk. The initial lesion started on his left knee at 6 months of age. The lesions became more erythematous on hot days or in warm temperature environments, and were otherwise asymptomatic.
On examination, he had multiple yellow-brown flat macules scattered over the trunk and limbs which become more inflamed on scratching.
Urticaria pigmentosa, also known as maculopapular cutaneous mastocytosis, is due to abnormal collection of mast cells in the skin causing brown patches and freckles. It is the commonest type of cutaneous mastocytosis.
It commonly affects infants, with first patches appearing at a few months of age. In young children, it is common for the patches to blister when rubbed.
50 to 70% of cases undergo spontaneous resolution before adolescence.
Most children with urticaria pigmentosa do not require any treatment.
Treatment modalities include:
Children with urticaria pigmentosa may develop anaphylaxis or anaphylactoid reactions to bee and wasp stings, hence it is advisable for them to carry an injectable adrenaline (epinephrine) kit.
