SLC52A3 and riboflavin transporter deficiency: 25 Heterozygous FIG4 mutations have been associated with adult-onset amyotrophic lateral sclerosis but without optic atrophy.26 We found the heterozygous c.1371C>G, p.(Phe457Leu) mutation in SLC52A3 in a 19-year-old man with Brown-Vialetto-Van-Laere syndrome, who responded well to riboflavin therapy.