Abstract
Biotinidase deficiency (BTD) is an autosomal recessive disorder and causes the deficiency of four biotin-containing carboxylases. The prevalence is estimated at 1 in 60 000 births. BTD is associated with a wide spectrum of clinical manifestations, including abnormalities of the neurological, dermatological, immunological, and ophthalmological systems. Spinal cord demyelination as a manifestation of BTD has been infrequently described. CASE PRESENTATION: The authors present a case of 2.5-year-old boy complained of progressive weakness in all four limbs, with difficulties in breathing. CLINICAL DISCUSSION: Abdominal examination revealed hepatomegaly and splenomegaly. Also, her parents were first-degree cousins. Therefore, tandem mass spectroscopy and urine organic acid analysis were planned to exclude metabolic disorders. Urinary organic acid analysis revealed elevated levels of methylmalonic acid and 3-hydroxyisovaleric acid. Serum biotinidase activity was found to be 3.9 nmol/min/ml. Oral biotin at a dose of 1 mg/kg daily was initiated. A marked improvement of his neurological deficit was noted over a period of 15 days after treatment and cutaneous manifestations resolved within 3 weeks. CONCLUSION: Myelopathy due to BTD is a challenging diagnosis. Spinal cord impairment is a rare complication of this disease and is frequently unrecognized. BTD should be included in the differential diagnosis of children presenting with demyelinating spinal cord disease.