TTC19 and Leigh syndrome: Mutations in TTC19 have been associated with heterogeneous clinical presentations, including early (Ghezzi et al., 2011) or late-onset ataxia (Nogueira et al., 2013; Morino et al., 2014), cognitive impairment (Ghezzi et al., 2011), slowly progressive developmental delay/regression due to necrotizing encephalomyopathy (Leigh syndrome; Atwal, 2013) and psychiatric symptoms (Nogueira et al., 2013).