Focal segmental glomerulosclerosis and concurrent glomerular microangiopathy after long-term imatinib administration

A 79-year-old Japanese man was admitted to our hospital because of proteinuria and kidney dysfunction. He was diagnosed with chronic myeloid leukemia 13 years before and was treated with imatinib. Deep molecular response was achieved but he developed 1+ proteinuria in the first year, which gradually worsened thereafter. Imatinib was discontinued 12 years later but proteinuria and kidney dysfunction were progressive. Percutaneous kidney biopsy revealed mild mesangial hyper-cellularity and matrix increase, swelling of endothelial cells, and partial double contours of glomerular tufts. Subendothelial edema in the interlobular artery was also noted. Immunofluorescence was not remarkable. Electron microscopy revealed endothelial injury with severe sub-endothelial edema. Since imatinib had already been discontinued, conservative therapy with maximal dose of azilsartan was administered. A second biopsy was performed 1 year later because of further deterioration of kidney function, which revealed markedly increased global glomerulosclerosis and severe interstitial fibrosis and tubular atrophy. Segmental glomerulosclerosis with podocyte hyperplasia was also observed. Electron microscopy revealed glomerulosclerotic changes and partially attenuated endothelial injury. Two and a half years later, proteinuria reduced, progression of kidney dysfunction slowed, and he was independent on dialysis therapy. Molecular response of chronic myeloid leukemia was also maintained. The clinical course suggested that endothelial and podocyte injuries were induced by imatinib, and that the nephrotoxic effects lasted for a few years after discontinuation.