A case diagnosed with IgA nephropathy during a complete remission of minimal change nephrotic syndrome treated with rituximab.

We herein report a case of IgA nephropathy in a 20-year-old male who maintained a complete remission of minimal change nephrotic syndrome (MCNS) through the administration of rituximab (RTX). He was diagnosed with nephrotic syndrome at 4 years of age. After he relapsed frequently, he was diagnosed with MCNS at 8 years of age based on the findings of a kidney biopsy. At 13 years of age, RTX therapy was initiated to maintain a complete remission after steroid treatment. MCNS recurred twice, including the time in which the interval between the RTX administrations was long. Whenever he relapsed, remission induction was achieved using steroids, and remission maintenance was achieved using RTX. Five months after the 7th RTX administration, the serum IgA level started to increase. After the 9th RTX administration, he demonstrated microhematuria despite the urinary protein level indicating complete remission. At the 10th administration, the urinary protein and the red-blood cell casts were also observed. A renal biopsy was performed 84 months after the initial administration of RTX, and the patient was diagnosed with complications of IgA nephropathy. RTX is not considered to be a useful treatment for IgA nephropathy. The reasons for this are due to the fact that IgA1 does not decrease even following the administration of RTX, because B cells residing in the mucosa may not be deleted by RTX, and IgA production may also continue due to the presence of CD20^- long-lived plasma cells. Even when administering RTX, if there are findings of glomerulonephritis on urine testing, the possibility of IgA nephropathy must be considered.