SDHB and Leigh syndrome: While positive muscle biopsy findings such as COX, SDH deficiency (Sonam et al., 2014), ragged red fibers (RRF), and atrophy of muscle fibers (Sofou et al., 2014) have been used as a diagnosis for LS, non-specific myopathic changes and negative findings have also been reported in patients with LS (Wei et al., 2018).