Urticaria Pigmentosa

The parents of a 6-year-old boy with a generalized rash sought medical care for the child. The outbreak began 2 years earlier on the boy's abdomen and spread over the entire body; oral antihistamines had been prescribed for the itching. The patient had no history of allergy, insect bite, fever, or GI symptoms. His vital signs were normal.

Dr Sunita Puri of Decatur, Ala, diagnosed urticaria pigmentosa, a common skin manifestation of mastocytosis. Histologic examination confirmed the diagnosis.

The characteristic lesions are reddish brown, frecklelike, hyperpigmented macules and papules that arise on the trunk and extremities; palms, soles, face, and scalp may be spared. Lesions exhibit Darier sign, which occurs when mild trauma, such as scratching and rubbing, releases histamine granules that cause urticaria and erythema around the macule. The pruritus associated with this condition may be exacerbated by spicy foods; hot baths; alcohol intake; temperature changes; and certain drugs, such as aspirin, codeine, opiates, and polymyxin B.

The mast cell infiltration of the skin that characterizes urticaria pigmentosa may also affect other organs, including the liver, spleen, lymph nodes, and bone marrow. Although mast cell disease in children is generally limited to the skin and often resolves by adolescence, patients in this age group need to be observed closely for possible systemic involvement.

H1- and H2-receptor antagonists may be used to relieve itching. A topical corticosteroid, 0.05%, can be applied and covered with plastic film for 8 hours each day for 8 to 12 weeks; the lesions may resolve, but they recur after therapy is discontinued.

This patient's rash responded to treatment with H1- and H2-receptor antagonists and corticosteroids; the parents were reassured that their son experienced only cutaneous manifestations of the disease and the prognosis was good.