Late Presentation of Biotinidase Deficiency with Acute Visual Loss and Gait Disturbance

The document described a case of a 5-year-old girl with an unusual presentation of biotinidase deficiency, which typically manifests in infancy or early childhood with symptoms like seizures, hypotonia, ataxia, hearing loss, dermatitis, and alopecia. However, this patient experienced acute visual loss due to optic atrophy and gait disturbance with lower-limb pyramidal signs, without seizures or issues with skin, hair, hearing, or intellect. Biochemical tests confirmed biotinidase deficiency, and she responded well to biotin therapy. The study suggested considering biotinidase deficiency in children with unexplained bilateral optic neuropathy, especially if accompanied by gait disorders.