Narrowing down a broad differential diagnosis
Our cas a ase was made somewhat challenging by the patient’s darkly pigmented skin color, which made any erythema and other cutaneous signs less visible. The differential was broad and included postinflammatory hyperpigmentation from eczema, multiple congenital nevi, sarcoidosis, leprosy, and cutaneous tuberculosis, all of which can be eliminated by performing a biopsy of the lesion.
Diagnostic criteria include biopsy and laboratory findings
In addition to a skin biopsy, initial assessment in cases of suspected cutaneous mastocytosis should include a complete blood cell count with differential, liver function tests (+/- liver ultrasound), a serum tryptase level, and a peripheral smear. Serum tryptase levels > 20 ng/mL have been shown to correlate with a higher probability of systemic mastocytosis. Higher tryptase levels also correlate with severity of disease in children.5
Treatment focuses on minimizing mast cell degranulation
Due to the relatively benign course of cutaneous mastocytosis, the mainstay of treatment is focused on minimizing mast cell degranulation to control subsequent symptoms. Avoiding precipitating factors such as temperature extremes, external stimulation of lesions, dry skin, infection, and certain medications (eg, nonsteroidal anti-inflammatory drugs, aspirin, morphine, polymyxin B sulphate, anticholinergics, some systemic anesthetics) that can stimulate mast cell degranulation is encouraged.2 H1 and H2 antihistamines are the first-line treatment for mild to moderate symptoms. In refractory cases, leukotriene receptor antagonists or oral cromolyn sodium may be considered.2
Regular follow-up every 6 to 12 months should be established after diagnosis.1 If symptoms persist into adulthood or concern for disease progression is high, a bone marrow biopsy is recommended.1
Our patient
Our patient’s laboratory results revealed a normal serum tryptase level (3.4 ng/mL; reference range < 11.5 ng/mL) and complete blood cell count. A complete metabolic panel demonstrated elevated and high-normal liver function tests with alanine aminotransferase (ALT) at 111 u/L (reference range, 10–40 u/L) and aspartate aminotransferase (AST) at 55 u/L (reference range, 7–56 u/L).
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