Shortness of breath, syncope, and cardiac arrest caused by systemic mastocytosis.

During a 3-month period, a 33-year-old man presented to the emergency department on 4 occasions with dyspnea, palpitations, and syncope. His initial presentation was accompanied by acute myocardial injury and ventricular fibrillation. An extensive evaluation spanned the 3 months and included echocardiography, cardiac catheterization, electrophysiology study, tilt-table evaluation, pulmonary angiography, electroencephalography, and serum and urine analysis. Diagnosis eluded clinicians until a rash was recognized to be urticaria pigmentosa, and biopsy of the rash then implicated mastocytosis. Since the initiation of pharmacotherapy nearly 5 years ago, the patient has remained asymptomatic. This case demonstrates that systemic mastocytosis can present as recurrent syncope and even as cardiac arrest. Diagnosis of this rare but potentially fatal disease is made particularly challenging by its protean manifestations.