ClinVar

Karadimas et al. (2000) identified a G-to-A substitution at mitochondrial nucleotide 5920 resulting in a trp-to-ter mutation in the MTCO1 gene. The mutation was identified only in COX-deficient skeletal muscle fibers from a 33-year-old man who suffered from recurrent myoglobinuria since childhood. Serum CPK levels ranged from 15,000 to 38,000. The mutation was heteroplasmic and abundantly present in COX-negative fibers but less abundant or absent in COX-positive fibers; it was not found in blood or fibroblasts from the patient or in blood samples from the patient's asymptomatic mother and sister. The sporadic occurrence of this mutation in muscle alone suggested that it arose de novo in myogenic stem cells after germ-layer differentiation.