Table 1.

Genetic classification of mitochondrial diseases.

Defect Location	Mode of Inheritance	Genetic Diseases and Their Characteristics	Biochemical Analysis
nDNA defect
Tissue-specific genes	Mendelian	Tissue-specific syndrome	Tissue-specific single enzyme lesion
Non tissue-specific genes	Mendelian	Multisystem disease	Widespread enzymatic lesions
mtDNA defect
Point mutation	Maternal inheritance	Multiple systems, impurities	Specific single enzyme lesion Widespread enzymatic lesions
Deletion	Distribute	PEO, KSS, Pearson	Widespread enzymatic lesions
NDNA and mtDNA combined defects
Multiple mtDNA deletions	AD/AR	PEO	Widespread enzymatic lesions
MtDNA deletion	AR	Myopathy, liver disease	Tissue-specific multi enzyme lesions

Note: PEO: progressive extraocular muscle paralysis; KSS: ophthalmic myopathy; Pearson: bone marrow/pancreatic syndrome; AD: autosomal dominant; AR: autosomal recessive.