Myeloma Cast Nephropathy an Unusual Association with HIV Infection Presenting with Renal Dysfunction

Human immunodeficiency virus (HIV)-associated renal disease is a pan-nephropathy, causing glomerular, tubular, and interstitial changes. The common lesion is the collapsing variant of focal segmental glomerulosclerosis. Multiple myeloma presenting as light chain cast nephropathy in an HIV-positive patient is very rare. A 45-year-old female retropositive patient presented with one episode of hematuria. Kidney biopsy was performed with a clinical diagnosis of acute interstitial nephritis (AIN). Biopsy showed unremarkable glomeruli. Tubules were dilated and showed a few periodic acid-Schiff (PAS) positive and many PAS-negative fractured casts surrounded by histiocytic reaction. Immunofluorescence and immunohistochemistry (IHC) showed lambda restriction by the casts. Bone marrow aspirate showed an increase in plasma cells, and the biopsy showed nodular aggregates of atypical plasma cells, which showed lambda restriction by IHC. PAS-negative fractured tubular casts are known to be associated with HIV-related nephropathy and need detailed hematological workup to rule out an associated plasma cell dyscrasia.