A 65-year-old man presented to the emergency department with hemoptysis and hematuria. During the preceding 3 weeks, he had developed fevers, weakness, and myalgias that were increasingly debilitating. He subsequently developed frank hemoptysis and gross hematuria over 3 days. He denied contact with persons who were ill, recent travel, or dental procedures. His past medical history was unremarkable except for elevated serum cholesterol levels, for which he had been taking simvastatin for many years.

On presentation, he was acutely ill, with a temperature of 38.8°C, a pulse of 90 beats per minute, a blood pressure of 132/88 mm Hg, and a respiratory rate of 18 breaths per minute. Examination of the head and neck revealed episcleritis and no oral ulcers. Examination of the heart was normal. Chest examination demonstrated bilateral coarse breath sounds with diffuse rhonchi. Skin examination revealed palpable purpura over the extensor surface of the right elbow.

Laboratory studies included the following values: serum urea nitrogen, 158 mg/dL; creatinine, 11.7 mg/dL; total leukocyte count, 16.1 × 10³/mL; and erythrocyte sedimentation rate, >130 mm/h. Urinalysis was notable for 35 red blood cells per high-power field. A chest radiograph showed patchy infiltrates in the right upper and lower lobes. An electrocardiogram (ECG) revealed normal sinus rhythm at a rate of 94 beats per minute with normal intervals.

The patient was admitted to the hospital with a presumptive diagnosis of vasculitis. He was treated with broad-spectrum antimicrobial agents, prednisone, and cyclophosphamide, in addition to beginning hemodialysis. Antimicrobial therapy was discontinued when blood cultures remained negative at 48 hours. The clinical diagnosis of Wegener’s granulomatosis was confirmed by an antinuclear cytoplasmic antibody titer of 1:80 and antiproteinase 3 (PR3) antibodies of 143 units (positive >30 units). A skin biopsy specimen demonstrated a small vessel vasculitis consistent with the diagnosis.

The patient’s symptoms improved gradually, and he was discharged on day 13 with outpatient hemodialysis. During the next 3 days, his strength increased, and he was able to walk longer distances. On the fourth day after discharge, he suffered a ventricular tachycardic arrest at the initiation of hemodialysis. He was admitted to the intensive care unit after a prolonged resuscitation effort, but he remained unresponsive. His ECG was unchanged, and troponin I assay did not suggest myocardial infarction. Blood cultures remained negative. A transthoracic echocardiogram demonstrated normal left ventricular function and no valvular abnormalities. After 10 days, he showed no neurologic improvement. The family decided to withdraw ventilatory support, and he died quickly.

What is the diagnosis?