A 32-year-old man was admitted to the Instituto Nacional de Ia Nutricion Salvador Zubiran for evaluation of chronic renal failure and severe hypertension. The patient's history included frequent episodes of pharyngitis during childhood. Five years before admission he noticed left lumbar pain, malaise, and weakness. Two years later he developed frontal headaches with blurred vision; blood pressure was 220/140 mm Hg. Antihypertensive treatment was prescribed but the patient stopped taking the medication when he began feeling better. Several weeks before admission he developed 2 to 3 episodes of nausea and vomiting per day, diarrhea, gingival bleeding, and epistaxis. On admission, physical examination revealed a blood pressure of 220/ 150 mm Hg; pulse, 84/mm; respirations, 14; temperature, 36.TC; and weight, 68.9 kg. The optic fundi showed arteriolar narrowing, arteriovenous nicking, a few exudates, and small hemorrhages. The cardiac apex was in the fifth intercostal space 10 cm left of the midsternal line. A grade ll/IV systolic murmur, audible at the base, radiated to the left sternal border. Peripheral pulses were normal and synchronous, and no edema was present. There was no asterixis. Laboratory findings revealed the following: hemoglobin, 6.7 g/dl; white blood cell count, 8300/mm3; serum sodium, 132 mEq/liter; potassium, 5.4 mEq/liter; chloride, 84 mEq/liter; BUN, 255 mg/dl; creatinine, 24 mg/dl; calcium, 8.2 mg/dl; phosphorus, 15.2 mg/dl; total