A child with urticaria pigmentosa: positive Darier’s sign
The present case has been reported in BMJ.

A 3-year-old boy presented to a paediatric consult with a rash consisting of reddish-brown non-pruritic spots. This rash initially appeared in his first months of age, with no identified triggers or associated symptoms and had been previously interpreted as eczema.

Skin examination revealed irregularly bordered, hyperpigmented, cafe-au-lait macules on his trunk, neck and right forearm, the largest around 2 cm in diameter. Rubbing one of the skin lesions elicited localised erythema—positive Darier’s sign.

Laboratory investigation showed both normal blood count and serum tryptase levels. He was diagnosed with urticaria pigmentosa (UP), a type of cutaneous mastocytosis. The patient is currently asymptomatic, without new skin lesions.

Learning points
• Searching for Darier’s sign is essential in the presence of typical brownish spots/macules in a child.

• If cutaneous mastocytosis is suspected, serum tryptase is an important marker of systemic mastocytosis and/or severe mediator release.

• Although urticaria pigmentosa has a good prognosis, parents should be informed of the potentially severe effects of massive mastocyte degranulation and its triggers.

Read more here: http://casereports.bmj.com/content/2018/bcr-2018-226189.full