SDHB and Mitochondrial myopathy: Light microscopic examination of the paraspinal muscle biopsy showed evidence of a mitochondrial myopathy, with frequent well-developed ragged red fibers demonstrated on trichrome stain and subsarcolemmal crescents (mitochondrial aggregates) on NADH and SDH stains; a significant proportion (approximately 6%) of muscle fibers was COX-negative (Figures 2a-c).