The patient had been in his usual h

The patient had been in his usual health until approximately 2.5 months earlier, when pain developed in his elbows, knees, hips, and wrists shortly after he returned from a rafting trip in Montana. He took ibuprofen and naproxen, with minimal improvement. After several days, he went to the emergency department at another hospital. Doxycycline was prescribed for 3 weeks. Serologic testing for Lyme disease was reportedly negative, but he completed the antibiotic course.Nine weeks before the current evaluation, the patient returned to the other hospital with weakness and diaphoresis. On examination, the pulse was 140 beats per minute and irregular, and the systolic blood pressure was 80 mm Hg. A diagnosis of paroxysmal atrial fibrillation was made. Diltiazem and intravenous fluids were administered, and normal sinus rhythm resumed. The patient was discharged home, taking lisinopril and acetylsalicylic acid. One week after discharge, swelling of the tongue, diaphoresis, and shortness of breath developed, and an urticarial rash appeared on his arms, trunk, and hips. He was admitted to a second hospital, where a diagnosis of angioedema, possibly due to lisinopril allergy, was made. Atrial fibrillation had recurred. Lisinopril was stopped, and metoprolol tartrate was administered. Cardioversion was performed, with restoration of sinus rhythm.Table 1.Laboratory Data.Approximately 7 weeks before the current evaluation, he was seen in the outpatient clinic at this hospital. The vital signs were normal. Urticarial lesions were present on the arms, trunk, and hips, and petechial lesions were present on the legs. The serum level of sodium was 131 mmol per liter (reference range, 135 to 146), and the level of chloride was 96 mmol per liter (reference range, 99 to 111). Measurements of other electrolytes, calcium, glucose, iron, total iron-binding capacity, thyrotropin, and cortisol (measured in the afternoon) were normal. Testing for antibodies to Borrelia burgdorferi was negative; other laboratory-test results are shown in Table 1. Blood cultures were sterile.