Urticaria pigmentosa

Are the tan macules on a 15-year-old girl’s forehead freckles?

University of Virginia

Dr Marchetti is a chief resident of dermatology and Dr Wilson is associate professor of dermatology at the University of Virginia School of Medicine in Charlottesville.

KIRK BARBER, MD, FRCPC––Series Editor: Dr Barber is a consultant dermatologist at Alberta Children’s Hospital and clinical associate professor of medicine and community health sciences at the University of Calgary in Alberta.

Urticaria pigmentosa

Urticaria pigmentosa Case: A 15-year-old healthy girl with bilateral tan macules on the lateral forehead and scalp presents for evaluation (A). She had previously been told these were freckles. The lesions were first noted at 5 years of age. Occasionally, they became itchy, red, and swollen. She denies headaches, diarrhea, shortness of breath, and abdominal pain. Her most recent complete blood cell count was normal. Upon vigorous rubbing of a lesion, a wheal and flare response is observed (B).



What are these lesions?

A. Langerhans cell histiocytosis.

B. Multiple juvenile xanthogranulomas.

C. Urticaria pigmentosa.

D. Acne scars.

E. Ephelides (freckles).


(Answer on next page.)


Urticaria pigmentosa

Answer: C. Urticaria pigmentosa

Urticaria pigmentosa is the most common form of cutaneous mastocytosis and represents 60% to 90% of childhood cases. Lesions typically begin within the first few weeks of life and are characterized by yellowish-brown to yellowish-red macules, papules, or nodules (A).

With mild trauma, such as scratching or rubbing, itching and urtication with surrounding erythema usually develop (Darier sign) (B). Pigmentation and evidence of skin lesions generally disappear before puberty.

The lesions in this case have an unusual distribution on the face and scalp, areas which are commonly spared. Another uncharacteristic feature of these lesions is their persistence into adolescence. The patient’s history, physical, and laboratory findings reveal no signs of systemic involvement, thus further workup is not indicated at this time.

Physical and chemical stimuli (medications) that induce mast cell degranulation should be avoided. Antihistamines may be used for symptomatic relief of urticaria, pruritus, and flushing. Photochemotherapy (UVA light therapy and psoralen) or topical corticosteroids may help induce clearance of skin lesions. Because spontaneous resolution occurs in the vast majority of patients without systemic disease, treatment is not routinely recommended. This patient opted to continue observation of the lesions.