Background: Riboflavin transporter deficiency (RTD), formerly known as Brown-Vialetto-van Laere syndrome, is an early-onset neurodegenerative disorder with distinctive phenotypes. RTD is caused by mutations in either the SLC52A2 or SLC52A3 genes that encode riboflavin transporters RFVT-2 and RFVT-3, respectively. Methods: This was a 3-year retrospective case review from the Cure RTD International Registry. Results: 73 individuals (~60% female, 14 deceased) from 56 families had genetically confirmed RTD Type 2, including 30 novel SLC52A2 mutations (24 missense, 2 nonsense, 4 deletion). The mean ages at symptom onset and at diagnosis were 2.4 years (SD 1.5, range 0.25–8, n=63) and 12.0 years (SD 10.2, range 0.75–52, n=56) respectively. Most common presenting symptoms were sensory ataxia (n=43), sensorineural hearing loss (n=22), nystagmus/visual loss secondary to optic atrophy (n=14), upper limb weakness (n=11), and respiratory insufficiency (n=9). Treatment included high dose riboflavin, other supplements, and supportive care; 7 individuals required transfusions for anemia pre-riboflavin treatment and 17 (25%) received a cochlear implant. The minimum prevalence of RTD was estimated to be 1 per million, with >100 new cases each year. Conclusions: This is the largest case series of RTD to date. Early recognition and prompt riboflavin treatment is essential for survival and optimal outcome.
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