Diagnosis: Urticaria pigmentosa
Urticaria pigmentosa (UP), also known as cutaneous mastocytosis, is characterized by the presence of pigmented macular and/or papular lesions associated with severe pruritis that can appear on any part of the body. With increased scratching and/or exposure to heat, the lesions become elevated. This phenomenon is known as Darier’s sign. The urticarial lesions can progress to become fluid-filled blisters. UP can rarely progress to systemic mastocytosis and present with systemic symptoms that are more common in adults, including headache, fatigue, abdominal pain, diarrhea, and tachycardia.
UP has been associated with increased inflammatory mast cells that abnormally collect in the skin. Mast cells specialize in producing histamine. In UP, the overproliferation of mast cells, secondary to point mutations in proto-oncogene c-kit binding to mast cell growth factor (MCGF), leads to an abundance of inflammatory chemicals, which produces the characteristic itching and presenting symptoms.
Although the pathophysiology of UP is known, the exact etiology is unclear. Certain medications that can cause mast-cell degranulation have been implicated, such as aspirin, NSAIDs, narcotics, alcohol, and anticholinergics. Children with allergies such as asthma are known to have an increased predisposition to UP, which typically presents in the first year of life and is self-limited by adolescence. Some cases sporadically appear, but others may be secondary to genetic inheritance as an autosomal dominant trait.
Diagnosis of UP is made by the presence of the characteristic skin lesions but can be confirmed by microscopic evaluation. A positive Darier’s sign on physical exam and lab testing for elevated histamine can aid in the diagnosis. UP is often mistaken for moles or insect bites on initial presentation; however, the persistence of the lesions for months to years is a distinguishing factor.
Given the self-limiting nature of UP, the treatment is symptomatic and supportive. Topical steroids and antihistamines can be useful to treat severe pruritis. In addition, PUVA has been shown to be an effective treatment for UP in adults.
This case and photo were submitted by Dr. Parteek Singla and Dr. Damon McClain of Naval Hospital Camp Lejeune, N.C.
Dr. Bilu Martin is in private practice at Premier Dermatology, MD, in Aventura, Fla. More diagnostic cases are available at edermatologynews.com. To submit your case for possible publication, send an email to email@example.com.