• Christophe Carreau, Charline Benoit, Guido Ahle, Cécile Cauquil, Agathe Roubertie, Timothée Lenglet, Jeremy Cosgrove, Isabelle Meunier, Alice Veauville-Merllié, Cécile Acquaviva-Bourdain, and Yann Nadjar.
• Department of Neurology, Reference Center for Lysosomal Diseases, Neuro-Metabolism Unit, AP-HP, Hôpital Universitaire Pitié Salpêtrière, Paris, France.
• J. Neurol. Neurosurg. Psychiatr. 2020 Oct 21.

ObjectiveRiboflavin transporter deficiencies (RTDs), involving SLC52A3 and SLC52A2 genes, have recently been related to Brown-Vialetto-Van Laere (BVVL) syndrome, a hereditary paediatric condition associating motor neuropathy (MN) and deafness. BVVL/RTD has rarely been reported in adult patients, but is probably underdiagnosed due to poor knowledge and lack of awareness of this form of disease among neurologists. In this study, we aimed to investigate the phenotype and prognosis of RTD patients with late-onset MN.MethodsWe retrospectively collected clinical, biological and electrophysiological data from all French RTD patients with MN onset after 10 years of age (n=6) and extracted data from 19 other similar RTD patients from the literature.ResultsAdult RTD patients with MN had heterogeneous clinical presentations, potentially mimicking amyotrophic lateral sclerosis or distal hereditary motor neuropathy (56%), multinevritis with cranial nerve involvement (16%), Guillain-Barré syndrome (8%) and mixed motor and sensory neuronopathy syndromes (20%, only in SLC52A2 patients). Deafness was often diagnosed before MN (in 44%), but in some patients, onset began only with MN (16%). The pattern of weakness varied widely, and the classic pontobulbar palsy described in BVVL was not constant. Biochemical tests were often normal. The majority of patients improved under riboflavin supplementation (86%).InterpretationWhereas late-onset RTD may mimic different acquired or genetic causes of motor neuropathies, it is a diagnosis not to be missed since high-dose riboflavin per oral supplementation is often highly efficient.© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.

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