Amyloid cast nephropathy with systemic AL amyloidosis

Excerpt

A 68-year-old woman was admitted to our hospital with a high serum creatinine level of 3.4 mg/dL, anemia, and hypotension (77/44 mmHg). Serum and urinary immunoelectrophoresis detected Bence Jones-λ monoclonal protein. Bone marrow examination revealed 3–4% plasma cells, most of which were CD19-negative monoclonal plasma cells with dysplastic changes and λ-chain restriction. The level of serum κ-light chain was 41.8 mg/L and the λ-chain level was 4730 mg/L. Urinalysis showed proteinuria of 3.8 g/g creatinine, mostly non-albuminuric. Renal biopsy revealed tubulointerstitial nephritis with cast nephropathy. Direct fast scarlet staining was positive in the small arteries and the casts, but there was no evidence of glomerular deposits (Fig. 1a). Only λ-chain deposits in the casts were observed by light chain staining (Fig. 1b). Furthermore, amyloid deposits were found in the gastric mucosa and abdominal fat. The patient was diagnosed with systemic AL amyloidosis with acute kidney injury (AKI) caused by amyloid cast nephropathy. Three months after weekly bortezomib and dexamethasone therapy, her levels of serum creatinine and proteinuria markedly improved (1.5–1.7 mg/dL and 0.1–0.2 g/g creatinine, respectively). The λ-light chain level was also reduced by 98% and her blood pressure normalized. However, frailty caused by urinary tract infection and pneumonia made continuation of chemotherapy unfeasible after 3 years, and the patient died of multiple organ failure. On autopsy, there were few remaining amyloid casts.

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