Long-term parvovirus B19 infections with genetic drift after cord blood transplantation complicated by persistent CD4+ lymphocytopenia.

A 5-month-old girl was diagnosed with Langerhans cell histiocytosis and received unrelated umbilical cord blood transplantation at the age of 14 months. After cord blood transplantation, CD4(+) lymphocytopenia from unknown causes was observed, and persistent infections with human parvovirus B19 (B19) occurred. We performed repeated longitudinal genetic analysis for B19, which revealed 6 nucleotide mutations in B19 nonstructural protein regions in the patient. The resulting changes of the nonstructural 1 structure may have altered antigenicity of the virus and could play a role in the pathogenesis of persistent infection under immunocompromised conditions.