GTPBP3 and lactic acidosis: More recently, patients exhibiting hypertrophic cardiomyopathy and lactic acidosis as a consequence of a combined respiratory chain deficiency have been found to carry mutations in MTO1 (Ghezzi et al., 2012; Baruffini et al., 2013) and GTPBP3 (Kopajtich et al., 2014).