Case Report: Light chain amyloidosis in a patient with low-grade B-cell lymphoma

Light chain (AL) amyloidosis is typically associated with plasma cell dyscrasias but can rarely arise from low-grade B-cell non-Hodgkin lymphoma. Renal involvement may present with nephrotic-range proteinuria, acute kidney injury, edema, anasarca, and hypoalbuminemia. Recognizing lymphoma-associated AL amyloidosis is essential because diagnosis requires tissue confirmation, and treatment must target the underlying clonal B-cell disorder.

We report a rare case of severe renal AL amyloidosis in a patient with known low-grade B-cell non-Hodgkin lymphoma previously treated with rituximab. The patient presented with witnessed syncope, progressive peripheral edema, anasarca, and hypotension. Initial evaluation showed acute kidney injury with nephrotic-range proteinuria, including a urine protein-to-creatinine ratio greater than 10 g/g. Workup for autoimmune, infectious, and malignant causes of proteinuric kidney disease revealed positive hepatitis C antibody, mildly elevated serum lambda free light chains, a mildly decreased kappa-to-lambda ratio, and serum immunofixation positive for an IgM monoclonal lambda gammopathy. Renal biopsy demonstrated severe AL amyloidosis with predominant renal involvement. Bone marrow biopsy showed low-grade B-cell non-Hodgkin lymphoma involving 85% of the marrow, with CD20-positive immunophenotyping.

This case highlights a rare presentation of renal AL amyloidosis secondary to low-grade B-cell non-Hodgkin lymphoma. Persistent nephrotic-range proteinuria in patients with B-cell lymphoma, particularly with IgM lambda monoclonal gammopathy, should prompt evaluation for amyloidosis with renal biopsy and hematologic assessment.