Monoclonal Gammopathy of Renal Significance Triggered by Viral E Hepatitis.

Monoclonal gammopathy of undetermined significance does not have end organ damage, but a proportion of cases manifest with renal injury when it is called monoclonal gammopathy of renal significance (MGRS). Herein, we describe a case of acute hepatitis E infection, which precipitated the development of MGRS. The patient underwent kidney biopsy for elevated creatinine with clinical suspicion of drug-induced interstitial nephritis. On light microscopy, there were periodic acid-Schiff negative-fractured casts in tubules with giant cell reaction around them. The tubular epithelial cells showed intracytoplasmic bile pigment. On direct immunofluorescence, casts showed kappa restriction. A diagnosis of bilirubin proximal tubulopathy and light chain cast nephropathy was made, and possibility of myeloma was suggested. On further evaluation, κ:λ ratio was 27, β2 microglobulin was 8036 ng/ml, and bone marrow examination showed 5% plasma cells. There were no bony lesions, and serum calcium was 8.6 mg/dl. The present case is unique in two aspects. First, the patient developed MGRS triggered by acute hepatitis E in less than a month. Second, the MGRS lesion was manifested in the form of light chain cast nephropathy.