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Adult-onset biotinidase deficiency: two individuals with severe, but reversible optic neuropathy
  1. Romain Deschamps1,
  2. Julien Savatovsky2,
  3. Catherine Vignal3,
  4. Matthieu Fisselier1,
  5. Apolline Imbard4,
  6. Barry Wolf5,6,
  7. Melinda Procter7,
  8. Olivier Gout1
  1. 1Department of Neurology, Fondation Ophtalmologique Adolphe de Rothschild, Paris, France
  2. 2Department of Radiology, Fondation Ophtalmologique Adolphe de Rothschild, Paris, France
  3. 3Department of Neuro-Ophthalmology, Fondation Ophtalmologique Adolphe de Rothschild, Paris, France
  4. 4Department of Hormonology and Biochemistry, Robert Debré Hospital, AP-HP, Paris, France
  5. 5Department of Research Administration, Henry Ford Hospital, Detroit, Michigan, USA
  6. 6Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan, USA
  7. 7Research and Development, ARUP Laboratories, Salt Lake, Utah, USA
  1. Correspondence to Dr Romain Deschamps, Department of Neurology, Fondation Ophtalmologique Adolphe de Rothschild, Paris 75019, France; rdeschamps{at}fo-rothschild.fr

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Introduction

Biotinidase is an enzyme that recycles biotin, a water-soluble vitamin essential as the coenzyme for four carboxylases that are involved in gluconeogenesis, fatty acid synthesis and in the catabolism of several branched-chain amino acids. Biotinidase deficiency (BD) is an autosomal recessively inherited disorder. Individuals with profound BD (<10% of mean normal serum biotinidase activity) present usually during early childhood with neurological disorders (seizures, hypotonia, ataxia, developmental delay, vision problems and hearing loss) and/or non-neurological findings (metabolic acidosis, respiratory difficulties, alopaecia and/or skin rash), that may progress to coma or death if untreated.1 Here, we present two cases of adult-onset BD with reversible optic neuropathy (ON).

Case reports

Patient 1

An 18-year-old man was referred with a 7-month history of bilateral progressive painless visual loss. He was born in France and his parents were from sub-Saharan Africa. There was no relevant familial medical history and no known consanguinity. On admission, decimal visual acuity (VA) of both eyes was <20/200 and ophthalmological examination showed bilateral, predominantly temporal, optic disc pallor. Goldmann perimetry demonstrated a bilateral centrocaecal scotoma. Spectral domain optical coherence tomography (Spectralis; Heidelberg Engineering, Heidelberg, Germany; SD-OCT) showed thinning of the peripapillary retinal nerve fibres layer (right eye, OD 78 µm and left eye, OS 73 µm) with preferential involvement of the temporal quadrant. Total macular volume measurements were normal. Visual evoked potential (VEP) and colour discrimination were not performed. His neurological examination was unremarkable. Brain MRI showed T2-weighted hyperintensities of both optic nerves and chiasm without Gadolinium enhancement and spinal MRI revealed bilateral longitudinally extensive high T2-signal intensities of anterior part of the spinal …

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