REEP4 and focal dystonia: Although rare cases of isolated BSP have been linked to THAP1 mutations [16], the genetic underpinnings of this important focal dystonia remained largely unknown until identification of a deleterious co-segregating REEP4 variant [GRCh38/hg38, NC_000008.11:g.22140245G> A, NM_025232.4:c.109C>T, p.Arg37Trp] in seven subjects with BSP or BSP+ from a 3-generation African-American BSP/BSP+ pedigree [17].