High on the Differential

A 48-year-old man who had received three cadaveric renal transplants had a 10-day history of painless edema of the legs. He was not short of breath at rest but had had moderate dyspnea on exertion for a week.The edema may be hydrostatic in origin, from either heart failure or other causes, or oncotic in origin, from hypoalbuminemia; bilateral deep venous thromboses would be unusual. The patient's shortness of breath may be caused by heart failure or fluid overload, but it could indicate lung infection. He is immunocompromised, so we need a broad differential diagnosis that includes opportunistic . . .