Biotinidase deficiency presenting as Neuromyelitis Optica Spectrum Disorder.

Biotinidase deficiency disorder is a rare inherited metabolic disorder with typical neurological manifestations of hypotonia, developmental delay, rashes, seizures, hearing and vision impairment. We present two cases with different and unusual clinical profiles, whose neuroimaging resembled Neuromyelitis Optica Spectrum Disorder. Case 1 was initially treated with immunomodulation with steroids and intravenous immunoglobulins, with partial improvement. However reinvestigation for worsening of symptoms showed more extensive changes on spine magnetic resonance imaging. Raised lactate and alanine levels on repeat cerebrospinal fluid testing resulted in further investigations that revealed a biotinidase deficiency. Case 2 presented mainly with respiratory symptoms: a barium swallow suggested bulbar dysfunction. Neuroimaging of brain and spine was similar to that in case 1 and the child was promptly investigated for and confirmed to have biotinidase deficiency. Both cases responded to biotin supplementation. It is important to be cognisant of atypical neurological presentations of biotinidase deficiency including those that mimic immune mediated neurodemyelination disorders, as biotinidase deficiency is potentially treatable.