Parvovirus B19-Induced Pure Red Cell Aplasia Several Years After Kidney Transplantation and Following a Transition From Everolimus to Tacrolimus.

A 57-year-old male patient, who underwent a preemptive living donor renal transplant from his mother 22 years earlier, was switched from everolimus to tacrolimus after 21 years because of development of proteinuria. Four months after transition of medication, the patient presented with anemia and reduced reticulocyte count, whereas leukocyte and platelet counts remained within normal limits. Investigation into the cause of anemia ruled out deficiencies in iron, folate, or vitamin B12, as well as inflammation, monoclonal gammopathy, hemolysis, and hypothyroidism. Gastroscopy and colonoscopy revealed no abnormalities. The patient showed a gradual increase in serum creatinine levels. Serological testing for human parvovirus B19 revealed a positive immunoglobulin M result. The patient was treated with intravenous immunoglobulin, after which hemoglobin levels began to rise within a few days. Three weeks after treatment, hemoglobin levels returned to baseline, and serum creatinine levels improved. A follow-up polymerase chain reaction test for human parvovirus B19 was negative. This case highlights the importance of maintaining vigilance for pure red cell aplasia caused by human parvovirus B19 infection, even long after kidney transplant, particularly when interventions are implemented that may increase the intensity of immunosuppression.