Online Mendelian Inheritance in Man (OMIM)

A number sign (#) is used with this entry because of evidence that lethal infantile mitochondrial myopathy may be caused by mutation in the MTTT gene (590090).

Yoon et al. (1991) attributed certain cases of lethal infantile mitochondrial myopathy (LIMM) to mutations in the mtDNA threonine tRNA gene (MTTT). The 2 patients in their study had severe respiratory chain enzyme deficiency and associated lactic acidosis and died within days after birth. Mutation was detected at nucleotide pair (np) 15924 in one patient and at nucleotide pair 15923 in the other. Both mutations occurred within the tRNA anticodon stem-loop structure. However, Brown et al. (1992) screened 3 LIMM and multiple control subjects for these mutations and reported that the nucleotide pair 15924 A-to-G mutation found in one of the patients was not the primary cause of LIMM. This Caucasian male died at 4 months of age of severe lactic acidosis with heart and muscle mitochondrial defects (Zheng et al., 1989). His mother had the same mutation, and both were homoplasmic. However, the mother showed no evidence of disease even after extensive biochemical, histologic, and clinical analyses. Furthermore, Brown et al. (1992) found the nucleotide pair 15924 mutation in approximately 11% (11/103) of Caucasian controls. The nucleotide pair 15923 mutation was not detected in 91 Caucasians, 35 Africans, and 57 Asians. Consequently, the role of this mutation in causing LIMM remained to be clarified.