Deteriorating neurological and neuroradiological course in treated biotinidase deficiency

: We report a 7-month-old female baby with recent onset of neurological manifestations and mucocutaneous candidiasis. Immunological findings were compatible with severe combined immune deficiency (SCID). Infectious etiology of the central nervous system (CNS) involvement was ruled out. Biotinidase deficiency was suspected because of the concomitance of neurological and immunological deficits and was confirmed by enzymatic assay. Comprehensive treatment, including bone marrow transplantation (BMT) and biotin, resulted in immunological recovery, but no improvement of neurological condition. Serial brain CT scans over a period of 2 1/2 years demonstrated profound progression of brain atrophy involving gray matter.