The clinical features of 78 symptomatic children with biotinidase deficiency were reviewed and the response to antiepileptic drugs and biotin therapy in 43 (55%) with seizures are reported from the Medical College of Virginia, Richmond, VA. Seizures were the presenting symptom in 30 (38%) patients, with onset between 2 and 24 months (mean, 8 months). Seizure patterns were generalized tonic-clonic or clonic in 56%, infantile spasms or myoclonic in 16%, and partial in only 5%. EEGs were abnormal in 16 (76%) of 21 patients tested; spike or epileptiform discharges were reported in 9. Antiepileptic drugs controlled seizures in 22 (51%) patients, but treatment was withdrawn without relapse after biotin therapy was initiated. Biotin orally, 5 to 10 mg daily, stopped seizures within 24 hours in 12 of 16 (75%) children whose seizures were uncontrolled by AEDs. Five infants died and 3 sustained permanent brain damage before the biotinidase deficiency was diagnosed. 
COMMENT. Early diagnosis by newborn screening is recommended by the authors. Biotinidase enzyme deficiency and a trial of biotin should be considered in infants or young children with poorly controlled seizures, especially in those with hypotonia, ataxia, skin rash, alopecia, metabolic ketoacidosis, or organic aciduria. Symptoms resolve rapidly after biotin therapy, but neurologic damage may be irreversible if diagnosis is delayed. (see Ped Neur Briefs, Jan 1990).