Crescentic Glomerulonephritis in a Patient With AL Amyloidosis: A Case Report

Crescentic renal amyloidosis is a rare complication of light-chain (AL) amyloidosis. We report the case of a 73-year-old man with AL amyloidosis involving the kidney and heart. At diagnosis, his creatinine was 0.94 mg/dL and proteinuria was 3.1 g/d. He achieved a hematologic very good partial response with ixazomib, cyclophosphamide, and dexamethasone. Creatinine briefly increased to 1.4 mg/dL after a coronavirus disease-2019 (COVID-19) infection but returned to baseline and remained stable for 11 months until receiving a COVID-19 vaccine. Following vaccination, creatinine progressively increased, and proteinuria increased to 8.5 g/d. Owing to worsening kidney function, therapy was switched first to daratumumab and subsequently to bortezomib. Although these agents further reduced lambda free light chains, creatinine continued to increase to 2.68 mg/dL, accompanied by a 25-pound weight loss. A kidney biopsy demonstrated diffuse amyloid deposition, cellular crescents, and fibrinoid necrosis in 2 glomeruli. Serologies for vasculitis were negative. Creatinine initially improved with dexamethasone, but treatment was discontinued owing to steroid myopathy. Cyclophosphamide was initiated, but creatinine increased further to 3.3 mg/dL. After switching to mycophenolate mofetil, creatinine steadily improved to 2.5 mg/dL. In this case, crescentic glomerulonephritis likely developed secondary to the COVID-19 vaccine, as evidenced by its lack of response to therapy targeting AL amyloidosis. This case emphasizes the importance of kidney biopsy in patients whose kidney function declines unexpectedly during successful treatment of systemic diseases such as AL amyloidosis.