Persistent developmental delay despite successful bone marrow transplantation for purine nucleoside phosphorylase deficiency

A 10-month-old girl with a history of recurrent candidiasis, developmental delay, and a fulminant varicella infection is described. The diagnosis of purine nucleoside phosphorylase (PNP) deficiency was suggested by a reduced level of serum uric acid and confirmed by measurement of PNP activity. A human leukocyte antigen-matched bone marrow transplantation resulted in immune reconstitution, but poor neurodevelopmental progression.