Dysproteinemia, proteinuria, and glomerulonephritis

CASE PRESENTATIONA 57-year-old woman was referred for evaluation of new-onset hypertension and proteinuria. The patient had developed lower extremity edema 3 months prior and had been treated with diuretics. Past medical history was significant for microscopic hematuria of many years' duration thought secondary to nephrolithiasis, longstanding arthritis of the hands and hips, depression, and deep venous thrombosis that occurred following arthroscopic surgery. There was no history of fever, skin rash, oral ulcers, alopecia, or photosensitivity.On physical examination, the patient was found to have a blood pressure of 150/94 mmHg. She was obese (height 5 ft and 6 inch, weight 262 lb). Cardiovascular and pulmonary examinations were unremarkable. There was no evidence of edema or hepatosplenomegaly. Her hands showed Heberden's and Bouchard's nodes bilaterally. The patient's medications included valsartan 320 mg daily, amlodipine 10 mg daily, raloxifene 60 mg daily, amitriptyline 25 mg daily, and potassium citrate 10 mEq twice per day for nephrolithiasis.Laboratory evaluation showed a total leukocyte count of 5600/mm(3) (normal range 4300-10 800/mm(3)) with normal differential, hemoglobin 13.4 g/dl (134 g/l) (normal range, 13-18 g/dl (130-180 g/l)), platelet count 238 000/mm(3) (normal range, 150 000-500 000 mm(3)), serum sodium 141 mmol/l (normal range, 135-145 mmol/l), serum potassium 4.6 mmol/l (normal range, 3.5-5.5 mmol/l), serum bicarbonate 28 mmol/l (normal range, 22-26 mmol/l), blood urea nitrogen 26 mg/dl (9.3 mmol/l) (normal range, 10-30 mg/dl (3.6-10.7 mmol/l)), serum creatinine 0.6 mg/dl (53 mol/l), estimated glomerular filtration rate 162 ml/min, albumin 2.5 g/dl (25 g/l) (normal range, 3.5-4.9 g/dl (35-49 g/l)), 24 h urine protein 1200 mg/day (normal range 0-150 mg/day), and cholesterol 170 mg/dl(4.4 mmol/l) (normal range, 130-200 mg/dl (3.36-5.17 mmol/l)). Serologic evaluation revealed an anti-nuclear antibody (ANA) titer of 1:640 with speckled pattern and normal serum complement levels. The following serologies were negative: anti-double-stranded DNA antibody, rheumatoid factor, serum cryoglobulins, hepatitis B surface antigen, and hepatitis C antibody. Urinalysis showed 2+ protein and 1+ blood. Microscopic evaluation revealed 5-10 red blood cells per high-power field, without red blood cell casts. Computerized tomography scan showed symmetric, normal-sized kidneys with multiple bilateral small non-obstructing calculi. Over the course of 3 month