A 51-year-old woman, who had both aortitis syndrome (Takayasu arteritis) and IgA nephropathy, presented with hypertension, fever, a high erythrocyte sedimentation rate, high C-reactive protein and serum IgG levels, proteinuria, and renal dysfunction. Renal arteriography showed stenosis and poststenotic dilatation at the origin of the right renal artery, as well as tortuosity of the left renal artery branches and marked atrophy of the left kidney. Renal biopsy showed IgA nephropathy with deposits of IgA, C3, and fibrinogen in the glomeruli and arteriolosclerosis. The present patient had human leukocyte antigen (HLA)-B 52, which is reported to be related to the aortitis syndrome, as well as HLA-DR 4, which is possibly related to IgA nephropathy, suggesting that HLA status may be involved in the pathogenesis of both diseases.