Spectrum of Renal Histopathological Changes in Multiple Myeloma

Abstract

Introduction: Renal involvement is very common in myeloma. The evaluation of renal status plays an important role in diagnosis and prognosis of patients with myeloma. The kidney biopsy will show various patterns of injury and the chronicity of the disease which help in planning the treatment options. Myeloma comprises a significant number of malignancies but no data regarding renal biopsy changes in myeloma is available from North Kerala, India. Aim: To describe the various morphological patterns of renal involvement in all myeloma patients who required a renal biopsy for evaluation of renal dysfunction. Materials and Methods: It was a retrospective, descriptive study conducted at Government Medical College, Kozhikode, a tertiary care centre from January 2016 to December 2019. A total of 63 patients of myeloma who underwent a renal biopsy for evaluation of renal dysfunction as the initial presentation or immediately after diagnosis were included in this study. Serum electrophoresis, skeletal survey, complete blood counts, bone marrow study and biochemical evaluation for serum creatinine, total protein, albumin globulin ratio were done in all patients. Data was analysed using standard analytical techniques with Statistical Package for the Social Sciences (SPSS) version 16.0 for Windows. Results: A total of 63 patients presented with renal dysfunction as initial symptom underwent renal biopsy. Most common age group of the study population was between 50 to 70 years. In 47 patients (74%) the renal dysfunction was the initial presenting symptom of myeloma. The presenting features were acute renal failure, nephrotic syndrome and acute nephritis. The renal biopsy findings included myeloma cast nephropathy, amyloidosis, proliferative glomerulonephritis and tubulointerstitial nephritis with cast nephropathy being most common pattern. Acute renal failure was more common in cast nephropathy while amyloidosis presented with nephrotic syndrome. The serum creatinine and calcium levels, plasma cell counts and degree of anaemia had a correlation with histological pattern of injury. Conclusion: Acute Kidney injury due to myeloma cast nephropathy is a medical emergency and prompt therapy with measures to reduce light chain load along with correction of dehydration can reduce renal damage and increase the patient survival. Many newly described entities like fibrillary and immunotactoid nephropathy can occur in myeloma and these can be identified only by electron microscopic evaluation of kidney tissue. They have important prognostic impact and significance when renal transplants are planned for. So renal biopsy supported by newer methods like immunohistochemistry and electron microscopy is a must to keep pace with newer advances in myeloma treatment like autologous stem cell transplantation.