You are asked to make a diagnosis in a 35-year-old man whose current complaint is shortness of breath on exertion. You are given a picture of a pruritic skin "rash" that he developed six years earlier while visiting friends in Puerto Rico. The rash resolved in a week without treatment, but six weeks later he developed fever, generalized adenopathy, hepatosplenomegaly, and pulmonary infiltrates (see chest x-ray #1). Your physical exam now shows evidence of right heart enlargement (parasternal heave, retrosternal dullness) and pulmonary hypertension (loud S2P, pulmonic click). You review his current chest film (chest x-ray #2). What is your diagnosis and what test(s) would you order to confirm your suspicions? How would you treat this gentleman?
DIAGNOSIS: Schistosoma mansoni infection (schistosomiasis). Carried by freshwater snails, S. mansoni cercaria can invade the skin causing an acute pruritic papular eruption at the site of inoculation ("swimmer's itch"). In previously sensitized individuals, lesions may be urticarial or vesicular, as in the presented case. The rash usually resolves within a week. Four to eight weeks after cutaneous invasion, an acute febrile illness (Katayama fever) may occur with generalized adenopathy, hepatosplenomegaly, eosinophilia, and pulmonary infiltrates (arrow head, chest film #1). In chronic S. mansoni infection, embolization of eggs to the pulmonary arterioles can cause endarteritis obliterans and severe pulmonary hypertension (chest film #2). Embolization to the portal system causes portal hypertension and cirrhosis. The diagnosis is established by finding eggs in the stool and/or in the muscle of a biopsied rectal valve. Praziquantel is the drug of choice for S. mansoni infections.
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