Light-chain nephropathy

Abstract

Case presentation A 65-year-old woman, first evaluated at New England Medical Center approximately 4 years ago for hypertension, was found to have glycosuria with a concomitant serum glucose level of 95 mg/dl. Serum uric acid was 2.1 mg/dl, the serum phosphorus was 1.8 mg/dl, and the patient had a hyperchioremic metabolic acidosis; the serum bicarbonate was 16 mEq/liter. Serum protein electrophoresis revealed a small monoclonal spike determined by immunoelectrophoresis to be a kappa light chain. Urinary protein electrophoresis revealed the same monoclonal light chain. Bone marrow biopsy and rectal biopsy were normal. Four months after first being seen, the patient was admitted for a percutaneous renal biopsy. Hematocrit, white blood cell count, and platelet count all were within normal limits. Creatinine clearance was 59 cc/mm. Plain films of the skull, pelvis, and spine revealed no evidence of myeloma. At the time of admission for the renal biopsy, she was treated only with neutral phosphate, 2 tablets orally 4 times daily. Physical examination revealed an elderly woman in no acute distress. Blood pressure was 150/90 mm Hg. The pulse was 72 and regular. Funduscopic examination was not performed. The question arose of slight enlargement of the right lobe of the thyroid. No breast masses were found. The lungs were clear. Cardiac examination was unremarkable. There were 2+ pulses throughout without bruits. Neurologic examination disclosed mild numbness to pinprick in the tips of all fingers, but no other abnormalities. Urinalysis revealed a specific gravity of 1.022; pH, 6; albumin, greater than 100 mg/dl; a trace of sugar; and 10 to 15 white blood cells, 0 to 2 red blood cells, and 4 to 6 epithelial cells per high-power field. Electrocardiogram was unremarkable save for nonspecific ST-T wave changes. Chest x-ray was within normal limits. Sodium was 145 mEq/Iiter; potassium, 4.2 mEq/liter;