Histological examination12 of muscle biopsies from individual S1, taken at 2.5 years, and from individual S2, taken at 7 months of age, demonstrated diffuse, profound reduction of histochemical COX reaction (Figures 2A and 2B), compared to a control muscle (Figure 2C). EM studies on the muscle biopsy from individual S1 showed the presence of enlarged mitochondria with osmiophilic inclusions and disorganization of the cristae (Figures 2D, S1A, and S1B).