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A 4-month-old girl with reddish brown spots
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A 4-month-old infant presented with an increasing number of asymptomatic red-brown “spots,” according to her mother. These began to appear at 3 months.
She had no fever, vomiting, diarrhea or upper respiratory symptoms. The rash seemed mildly pruritic. On exam, there were 10 scattered round-to-oval red-brown macules and papules dispersed over her chest, back and neck. When one of the lesions was vigorously rubbed with a pen, it developed a white wheal. A few minutes later, there was a red flare around the lesion.
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Answer
The answer is mastocytosis, subtype urticaria pigmentosa.
Mastocytosis is a disorder of mast cells and can develop at any age. It usually appears in the first weeks to months of life. The cause is unknown. In young children, the disease involves increased mast cells in the skin but rarely other organs. In older children (age at diagnosis, > 10 years) and adults, it is more likely to be a systemic disease. Mast cells contain histamine and other inflammatory mediators which, when triggered, are released into the skin, blood and other organs.
Cutaneous mastocytosis is characterized by the degree of skin involvement. The most common types in children are solitary mastocytomas, urticaria pigmentosa and diffuse cutaneous mastocytosis.
Solitary mastocytomas are collections of mast cells presenting with a single or multiple (usually five or fewer individual) orange- to red-brown plaques or nodules ranging from 0.5 cm to 3.5 cm in diameter. They typically appear within three months after birth. They may develop a “peau d’orange,” or an orange peel-like texture. The clue to diagnosis is the Darier’s sign, which is development of a wheal and flare following firm stroking of a lesion with dull edge of a pen or fingernail. The stroking leads to mast cell degranulation and histamine release. The lesion typically develops a raised, white wheal in the center and then a surrounding bright red flare within several minutes. The lesion may subsequently blister in children in the first year of life but does not lead to permanent scarring. Such lesions are often mistaken for bullous impetigo.
If there is enough histamine release, some patients may develop systemic symptoms including nausea, diarrhea, abdominal pain, flushing, pruritus, hypotension and rarely, respiratory symptoms of bronchospasm. Rarely, enough histamine is released to cause anaphylaxis and death. Treatment of choice is administration of oral antihistamines such as diphenhydramine. Epinephrine can be given in acute situations. Lesions typically involute over eight to 10 years.
Urticaria pigmentosa also occurs in infancy and is present in some patients at birth. Brown spots are typically present by 6 months of age in most patients and may involve mucous membranes. New lesions may develop for many years. They appear as hyperpigmented to red-brown, minimally elevated macules, papules and plaques ranging in size from 0.5 cm to 1.5 cm in a random distribution. Typically, the scalp, palms, soles and sun-exposed areas are spared. Lesions may become bullous in patients aged younger than 2 years. Darier’s sign is positive, and patients may complain of flushing, pruritus or dermatographism. Symptoms typically improve over time, and 50% of patients have resolution of lesions by adolescence. Although lesions become less and less symptomatic, the overlying pigmentation tends to persist.
Diffuse cutaneous mastocytosis is rare and more commonly associated with systemic symptoms of histamine release. This form involves diffuse infiltration of mast cells in the skin, and patients may be at risk for systemic disease. Skin may appear normal or have a thickened, red-brown appearance. Extensive blistering is not uncommon in infancy. Darier’s sign is difficult to elucidate in this type because of the extensive skin involvement. The disease is usually present by age 3 years and spontaneously resolves in most patients during early childhood, although dermatographism often persists. These children are at highest risk for systemic symptoms and even fatal hypotension and/or bronchospasm.
Diagnosis can be made with a careful history, physical exam and the pathognomic Darier’s sign on exam. Skin biopsy is confirmatory and shows collections of mast cells in the dermis. Diagnosis can be further confirmed by measuring serum tryptase — another mast cell mediator — or urine histamine and its metabolites. Bone marrow biopsy or gastrointestinal tract evaluation is usually unnecessary unless there are concerns for systemic disease. Most patients do not need further workup unless there is extensive disease, in which case a complete blood count with a blood smear and serum chemistries should be obtained.
Treatment includes avoiding triggers of histamine release when possible. These include sudden weather changes, hot beverages, hot baths, insect stings, mechanical irritation and certain infections. Drugs known to induce symptoms include but are not limited to: alcohol, nonsteroidal antiinflammtory agents, aspirin, polymyxin B, vancomycin, morphine, codeine and some local and general anesthetics. Anesthesiologists should be informed of the condition before any surgical procedures to avoid histamine-releasing agents. In addition, a nonsedating H1 blocker can be used for systemic symptoms. More severe symptoms may require a classic (sedating) H1 blocker and/or H2 blockers (good for gastrointestinal symptoms). In rare gastrointestinal cases, oral sodium cromolyn can be used. There is some evidence that treatment with high-potency topical steroids can reduce the reactivity of mastocytomas. If they are causing significant systemic symptoms, solitary mastocytomas can be surgically excised. EpiPens are recommended for patients with extensive disease, although all patients and their parents should be counseled about this possible complication. Further therapy such as phototherapy, steroids under occlusive dressing and immunologic agents are reserved for the specialist.
For more information:
- Marissa Perman is at Cincinnati Children’s Hospital Medical Center.
- Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. Philadelphia: Mosby; 2004:156-159.
- Heide R, Tank B, Oranje AP. Mastocytosis in childhood. Pediatr Dermatol. 2002;19:375-381.
- Paller AS, Mancini AJ. Hurwitz Clinical Pediatric Dermatology: A Textbook of Skin Disorders of Childhood and Adolescence. Philadelphia: Elsevier; 2006:225-229.
Spot the Rash is a monthly case study featured in Infectious Diseases in Children designed to test your skills in pediatric dermatology issues.