These diverse genetic disorders cause two main syndromes:
1. Myopathy, with onset usually in infancy (floppy baby syndrome) or childhood (muscular dystrophy-like presentation)
2. Hepatocerebral syndrome, defined above as a combination of brain and liver dysfunctions.
These are autosomal recessive diseases due to mutations in genes that encode proteins providing the building blocks and the upkeep of mtDNA.
They are progressive disorders often fatal in childhood and for which no specific or effective therapy is available.