Adult mitochondrial myopathy: very slowly progressive muscular damage of the limbs, often associated with multisystem damage and high mortality

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A retrospective study at the Mayo Clinic in Rochester (Minnesota, USA) was based on 94 cases of mitochondrial myopathy diagnosed in adulthood and followed up between 2005 and 2021:

  • the mean time between the first signs and diagnosis was 11 years and the median age at diagnosis was 48 years (range 32 to 63 years);
  • the most frequent phenotypes were multisystem involvement in 32% of cases, MELAS in 15%, limb-girdle myopathy in 14%, chronic external ophthalmoplegia in 13% and external ophthalmoplegia-plus also in 13% of cases;
  • the mutation affected mitochondrial DNA in 48 patients and nuclear DNA in 29; the genes most frequently involved were MT-TL1 in 27 cases and POLG in 17 cases;
  • skeletal muscle involvement of the limbs was found in 43% of cases, 69% had involvement of the central nervous system and 21% had cardiac involvement;
  • median follow-up was 4.25 years (from just over two years to eight years);
  • loss of muscle strength was moderate and slowly progressive, with the need for walking assistance on average 17 years after the onset of the disease;
  • thirty patients died on average 33.4 years after the onset of the disease, with cardiac involvement being associated with higher mortality.

 

Mitochondrial myopathies diagnosed in adulthood: clinico-genetic spectrum and long-term outcomes. Beecher G, Gavrilova RH, Mandrekar J et al. Brain Commun. 2024 Feb 14;6(2):fcae041.

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