A 53-year-old female was admitted to our department for one-month dizziness and fatigue.
On admission, physical examination showed BP of 130/80 and leg pitting edema.
Laboratory examinations showed hemoglobin 56 g/l, serum albumin 23.5 g/l, and creatinine 1.54 mg/dl. Urine test detected protein (3+) and no microscopic hematuria. The 24-hour total protein excretion of 3.41 g but the 24-h urine albumin exertion was only 0.6 g. Urine protein electrophoresis showed 51% of large-molecular proteins. Tests for hepatitis B and C, syphilis, antinuclear antibody, double-stranded DNA antibody, antineutrophil cytoplasmic antibody, anti-extractable nuclear antigen antibodies were negative. The anti-PLA2R level was 27.38 RU/ml (ELISA). The serum IgG was significantly elevated to 95.3 g/l. ESR was 121 mm/h. Immunofixation electrophoresis revealed monoclonal IgG κ. The serum free light chain κ and λ were respectively 12.62 mg/l and 8.62 mg/l with the radio of 1.464 and the urine free κ and λ were respectively 287.50 mg/l and 69.40 mg/l with the ratio of 4.1427. Skull x-ray showed multiple lytic lesions. Abdominal ultrasound showed renal hyperechogenicity. Bone marrow examination showed an elevated plasma cell fraction of 9.5% with κ restriction. Multiple myeloma (MM) was made.
Renal biopsy obtained five nearly-normal glomeruli with no hypercellularity, GBM thickening or projections. However, eosinophilic-strong and PAS-weak granules were observed within podocytes, endothelial cells, and tubular epithelial cells (Fig. 1). The immunofluorescence study displayed diffuse weak granular IgG (1+) and κ (1+) staining in glomeruli and tubules with IgG1 κ restriction (Fig. 1). Other staining, including IgG2, IgG3, IgG4, IgA, C3, C1q, Alb, λ, PLA2R, and THSD7A, were all negative. Electron microscopy showed diffusely-thinning GBM (< 250 nm) and various crystals within podocytes, endothelial cells, tubular epithelial cells and mesangium (Fig. 1). She was diagnosed as light-chain crystalline nephropathy.
The patient was treated with BCD regimen (bortezomib 2 mg, dexamethasone 20 mg, plus cyclophosphamide 0.45 mg on Days 1, 4, 8 and 11). After three cycles, serum creatinine decreased to 0.99 mg/dl and serum albumin increased to 37 g/l. The 24-hour protein also decreased to 0.9 g. The IgG level continuously decline to 36 g/l and the anti-PLA2R antibodies remained positive from 36.02 RU/ml to 41.76 RU/ml.