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A 64 year old man with a 15 year history of coronary artery disease and hypertension (treated with Hygroton 50mg/day), and a 5 year history of diabetes mellitus (treated with 25 units NPH insulin/day) was found to have 3+ proteinuria during a routine physical examination. Follow-up laboratory evaluation revealed:
9 g/day proteinuria,
2-3 RBC/hpf in the urine,
serum creatinine 1.2 mg/dL (106 umol/L),
creatinine clearance 77 mL/min (128 mL/s),
BUN 20 mg/dL (7.0 mmol/L),
cholesterol 300 mg/dL (7.76 mmol/L),
albumin 3.1 g/dL (31 g/L),
calcium 9.2 mg/dL (2.30 mmol/L),
phosphorus 4.3 mg/dL (1.39 mmol/L),
glucose 189 mg/dL (10.5 mmol/L),
uric acid 9.5 mg/dL (565 umol/L), and
normal LFTs.
He was referred to a nephrologist for evaluation and treatment. Physical examination revealed weight 81.2 kg, blood pressure 100/72 mm Hg, no retinopathy and 1+ pitting edema in the lower extremities. Laboratory data included:
12 g/day proteinuria,
8-10 RBC/hpf in the urine,
serum creatinine 1.2 mg/dL (106 umol/L),
creatinine clearance 94 mL/min (1.57 mL/s),
BUN 21 mg/dL (7.5 mmol/L of urea),
cholesterol 310 mg/dL (8.02 mmol/L),
albumin 2.9 g/dL (29 g/L),
calcium 8.6 mg/dL (2.15 mmol/L),
phosphorus 4.3 mg/dL (1.39 mmol/L),
uric acid 10.1 mg/dL (600 umol/L),
normal serum complement, and
negative ANA.
Urine protein electrophoresis demonstrated nonselective proteinuria and a monoclonal spike in the beta region with beta-gamma bridging (see Figure 1)). Serum and urine immunoelectrophoresis demonstrated an IgA lambda monoclonal immunoglobulin. Quantitative immunoglobulin assays revealed:
IgA 1270 mg/dL (12.70 g/L),
IgG 812 md/dL (8.12 g/L), and
IgM 40 mg/dL (0.40 g/L).
A bone marrow biopsy showed 7% plasma cells and no amyloid. Immunohistology demonstrated that most of the plasma cells contained IgA lambda. A rectal biopsy demonstrated no amyloid. A renal biopsy was performed.
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