A 5-year-old boy presented to the pediatric clinic with a history of itchy skin lesions since infancy. The lesions developed, lasted for a few days, and regressed with a residual brown pigmentation. The condition had been treated as eczema, with topical corticosteroid creams and diphenhydramine, with little relief.
His past medical history included hydrocephalus status after ventriculoatrial shunt placement, and epilepsy that was well controlled on levetiracetam. He had reached all appropriate developmental milestones. The family was otherwise healthy. There had been no known exposure to similar skin lesions or pets.
On physical examination, the patient had normal vital signs and was in no distress. His height and weight were both in the 50th percentile. A few erythematous, slightly raised lesions were scattered on his face, trunk, and extremities (A) and multiple areas of brown pigmentation across the back, chest, and extremities (B). When rubbed, the area became erythematous and raised, and the patient complained of pruritus. Findings from the rest of the physical examination were normal.
Based on findings from the history and physical examination, the boy received a diagnosis of urticaria pigmentosa.
When evaluating a skin lesion that evolves, it is helpful to see the different morphologies over time. Patients can bring along photographs of their rapidly changing lesions on their cell phone. An acute urticarial lesion that is healing with pigmentation raises the suspicion for urticaria pigmentosa.
Urticaria pigmentosa is a type of mastocytosis, a term applied to a group of disorders in which mast cells accumulate within tissue. Involvement can range from cutaneous to systemic. The 3 major types of mastocytosis in childhood are urticaria pigmentosa, solitary mastocytoma of the skin, and diffuse cutaneous mastocytosis.
Urticaria pigmentosa occurs in 2 distinct types, hereditary and nonhereditary. The hereditary type is rare and accounts for less than 2% of cases of childhood urticaria pigmentosa.1 Hereditary urticaria pigmentosa generally presents after 1 year of age, the lesions do not spontaneously resolve, and systemic involvement may be seen over time.
The patient in this case had the nonhereditary type of urticaria pigmentosa. The lesions generally appear before 1 year of age and can occur over the entire body, although the densest collection typically occurs over the trunk. The lesions develop as erythematous macules that heal with brown pigmentation. The Darier sign can be evoked, in which edema and an erythematous flare occur in response to stroking the lesion. This localized reaction is the result of histamine release from mast cell degradation secondary to minor trauma such as stroking the skin. Dermatographism also may be present. In most cases, the lesions spontaneously clear by the time a patient reaches the age of 7 years.1
A solitary mastocytoma generally is present at birth. These lesions have a red-brown appearance and usually are located on the trunk.
Diffuse cutaneous mastocytosis is a variant that occurs most commonly in infants. The infiltration of mast cells causes thickening of the skin; areas of greater infiltration cause nodules or plaques. Patients with diffuse cutaneous mastocytosis are more likely to have severe complications (eg, systemic involvement such as anaphylaxis and hypotension), but spontaneous resolution usually occurs by 5 years of age.2
Systemic mastocytosis can occur in up to 2% of patients with hereditary urticaria pigmentosa and must be considered in the presence of evidence of systemic involvement such as flushing, tachycardia, hypotension, diarrhea, vomiting, symptoms of peptic ulcer, and even splenomegaly and hepatomegaly. In extreme cases, liver involvement can lead to cirrhosis. Systemic involvement can include bony involvement; bone marrow aspiration and biopsy results will show an increase in mast cells within the bone marrow.1
Certain medications can lead to worsening of urticaria pigmentosa. Opioids, polymyxin B, and aspirin can induce bulla formation and even can lead to systemic symptoms.2 Tumor necrosis factor antagonists have been reported to trigger urticaria pigmentosa.3
Results of a skin biopsy can confirm the diagnosis but is not necessary if the clinical suspicion is high; systemic mastocytosis also has been associated with elevated serum tryptase levels.4
Treatment of this urticaria pigmentosa generally is supportive to control the symptoms. Systemic symptoms can be relieved with hydroxyzine hydrochloride. Topical corticosteroids can be effective treatment for solitary mastocytomas. For patients with systemic symptoms, epinephrine in autoinjector form should be prescribed in case of life-threatening emergencies. n
Vascular reactions: urticaria, erythemas, and purpuras. In: Weston WL, Lane AT, Morelli JG. Color Textbook of Pediatric Dermatology. 4th ed. Philadelphia, PA: Mosby Elsevier; 2007:265-266.
Ghiasi M, Ghanadan A, Jesri SB, Sotudeh S, Ramyar A. Diffuse cutaneous mastocytosis: report of a severe case with fatal outcome. Dermatol Online J. 2011;17(3):7.
Leloup P, Daviet V, Chiffoleau A, Dréno B. Urticaria pigmentosa after treatment with TNF antagonists: a case report. Arch Dermatol. 2011;147(12):1459-1460.
Vano-Galvan S, Álvarez-Twose I, De las Heras E, et al. Dermoscopic features of skin lesions in patients with mastocytosis. Arch Dermatol. 2011;147(8):932-940.