Multiple Facets of Multiple Myeloma in Kidney Biopsy: A Multicenter Retrospective Study.

Introduction: Multiple myeloma is a type of plasma cell dyscrasia, which causes clonal proliferation of plasma cells and deposition in various organ systems. At presentation, 50% of patients with multiple myeloma have kidney dysfunction, which is considered a poor prognostic indicator. Data on the histopathological manifestations of multiple myeloma are sparse. Objective: To look at the kidney histopathological lesions in patients with the clinical diagnosis of multiple myeloma. Materials and Methods: A retrospective analysis of all kidney biopsies in patients with the clinical diagnosis of multiple myeloma was performed from June 1, 2020 to May 30, 2022, from three tertiary care nephrology referral centers. Results: A total of 61 patients with multiple myeloma and biopsy-proven kidney involvement were included in the study. The mean age at presentation was 55.39 ± 11.91 years, with male predominance (male to female ratio -1.6:1). The most common lesion on kidney biopsy was myeloma cast nephropathy (72.1%), followed by light chain deposition disease (21.3%) and AL amyloidosis (18%). About 26% of patients had dual lesions on kidney biopsy, 3% had three types of lesions on kidney biopsy In 48% of patients, the diagnosis of multiple myeloma was made only after the kidney biopsy. Conclusion: Patients with multiple myeloma and kidney involvement should be biopsied as the type of histopathological lesion influences the treatment options and prognosis.