Bone marrow findings and examination of peripheral blood CD20 cells in late-onset neutropenia after rituximab administration for nephrotic syndrome

Abstract

Although late-onset neutropenia (LON) is known as a late complication after administration of rituximab (RTX), there is no report for the bone-marrow findings in nephrotic syndrome. In addition, the pathogenic mechanism of LON or Rituximab-associated late-onset neutropenia (R-LON) still remains unknown. In this study, we conducted bone marrow examination for the case with LON three months after RTX administration for refractory nephrotic syndrome. Later, we discussed the pathogenic mechanism of R-LON by the bone marrow findings and the transition of peripheral blood CD20 cells. The case was for a 7-year-old girl who received RTX administration (375 mg/m²/administration) four times for FRNS/SDNS. Yet, she had fever and Grade 4 agranulocytosis two and a half months after the last administration. We also found differentiation arrest findings only for myelocyte series in the bone marrow examination. The percentage of CD20-positive cells in peripheral blood was 0.05%, but it was changed to 1.5% after one month and 7% after two months as normal. From the above-described results, LON has developed right before B-cell recovery. Thus, after RTX administration, it needs to pay attention to leucocyte and differential leukocyte count before B-cell recovery.