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Biotinidase deficiency is an autosomal recessive condition in which the normal recycling of biotin is deficient. If untreated, infants with biotinidase deficiency will develop neurologic derangements including optic atrophy.1 We describe a case of optic neuropathy due to biotinidase deficiency in a 19-year-old man.
The patient was identified as having biotinidase deficiency on newborn screening and was provided with appropriate supplementation. However, at approximately age 10 years, supplements were discontinued. At age 19 years, he developed simultaneous bilateral vision loss over several weeks. There were no other neurologic symptoms. Family history was unremarkable. Social history was notable for occasional binge drinking since starting college 2 months prior to onset of symptoms. The patient had visual acuity of 20/70 OD and 20/25 OS, he identified 11 of 14 Ishihara color plates with each eye, the flicker fusion frequency was undetectable in the right eye and 9.5 Hz OS (reference range, >30 Hz), and visual fields showed bilateral cecocentral scotomas with respect of the vertical meridian (Figure 1). The pupils were briskly reactive to light with no relative afferent pupillary defect. There was mild optic disc pallor bilaterally and optical coherence tomography showed atrophy of the papillomacular bundle (Figure 2). Neurologic examination findings were otherwise normal. Findings on magnetic resonance imaging of the brain and orbits with contrast were normal. Biotin levels were undetectable and biotinidase activity was markedly reduced (0.2 U/L; reference range, 3.5-13.8 U/L). Genetic testing demonstrated a homozygous double mutation (D444H:F403V) predictive of profound biotinidase deficiency. He began treatment with biotin, 20 mg/d. The patient improved within 1 month. After 4 months, he had return of visual acuity to 20/20 OU and the flicker fusion frequency improved to 26.5 Hz OD and 28.8 Hz OS. Minor residual visual field defects remained (Figure 1) and color vision remained similar to his initial presentation. He continued to be stable after an additional year of follow-up.
Haines SR, Longmuir RA. Optic Neuropathy Due to Biotinidase Deficiency in a 19-Year-Old Man. JAMA Ophthalmol. 2014;132(2):228-230. doi:10.1001/jamaophthalmol.2013.6249