Other mutations of SDH subunits that have been implicated in neurodegenerative diseases include SDHA causing ataxia [63] and SDHA [64], SDHB [64], SDHD [65], and SDHAF1 [66] leading to leukodystrophy, yet these studies have been limited to few patients (Figure 2). This evidence concerns the gene SDHB and leukodystrophy.