TMEM240 and spinocerebellar ataxia type 21: In studies of patients from France, Germany, the Netherlands, Colombia, Japan, and China, mutations in TMEM240 have been found to cause spinocerebellar ataxia 21 (SCA21) with mental retardation, severe cognitive impairment, and hypokinetic and hyperkinetic movement disorders (Delplanque et al. 2014; Traschutz et al. 2019; Yahikozawa et al. 2018; Zeng et al. 2016).