SLC52A3-related Brown-Vialetto-Van Laere syndrome: a large cohort from the Arabian Peninsula.

SLC52A3-related Brown-Vialetto-Van Laere syndrome (BVVL) is a rare neurodegenerative disorder characterized by progressive motor and sensory impairment, with high mortality rate if left untreated. We hereby report the largest cohort with SLC52A3-related BVVL from the Arabian Peninsula. A total of 23 patients, 16 females and 7 males, with genetically confirmed BVVL diagnosis at two tertiary centers from the region were retrospectively reviewed. Most patients were clinically ascertained (13/23), while 10 patients were diagnosed pre-symptomatically. 20 patients were homozygous for SLC52A3: c.634C>T (p.Arg212Cys) variant and 3 patients were homozygous for SLC52A3: c.1325_1326del. Facial diplegia was the commonest clinical feature (12/13), while moderate to severe hearing loss and dysarthria were seen in (10/13) patients. Symptomatic patients were treated with riboflavin doses ranging between 15 and 100 mg/Kg/day, with a median of 26 mg/Kg/day. Pre-symptomatic patients were treated with doses lower than that (as low as 5 mg/Kg/day). Patients were followed for 6 months to 12 years, with a median of 4 years. Most patients have shown significant or near-total recovery with residual symptoms (11/13), while 9/10 patients diagnosed pre-symptomatically remained symptom-free, and 2 symptomatic patients showed complete resolution of symptoms. The study emphasizes the significant interfamilial and intrafamilial variability of BVVL, and it stresses the impact of early treatment with riboflavin in the prevention of morbidity and mortality associated with this condition. The study also provides the longest cumulative follow-up of pre-symptomatically treated patients reported to date, providing preliminary evidence for the role of riboflavin in the prevention of morbidities associated with this condition.