Table 3.

Summary of main clinical phenotypes of mitochondrial disorders, with relative clinical clues and genotypes.

TAG	Phenotype	Clinical features	Genotype
CPEO	Chronic Progressive External Ophthalmoplegia	Progressive bilateral ptosis and diffuse reduction in ocular motility	Large-scale mtDNA deletions OR multiple mtDNA deletions (due to mutations in TWNK, POLG, TK2, RRM2b, DGUOK genes or others) OR point mtDNA mutations
CPEO plus	Chronic Progressive External Ophthalmoplegia Plus	Progressive bilateral ptosis and ophthalmoparesis associated to multiple features of neuromuscular and multisystem involvement	See “CPEO” Genotype
KSS	Kearns-Sayre syndrome	Early onset CPEO with cardiac conduction block and pigmentary retinopathy, w/o multisystem involvement; Ataxia, Psychomotor regression	Large-scale mtDNA deletions
ADOA	Autosomal Dominant Optic Atrophy	Visual loss starting during 1st decade of life, color vision defects	nDNA mutations (OPA1–OPA3–OPA 4–5-8 gene)
MELAS	Mitochondrial Encephalomyopathy Lactic Acidosis and Stroke-like episodes	Seizures, Ataxia, Myoclonus, Psychomotor regression, Cortical blindness, Dystonia, Weakness, Sensorineural hearing loss, Short stature, Lactic acidosis, hemiparesis/hemianopia	tRNA point mutation (m.3243A > G)
MM	Other Mitochondrial Myopathy	All other combinations of muscle weakness w/o multisystem involvement	nDNA mutations OR mtDNA depletions OR mtDNA deletions