To evaluate the presence, amount and the possible function of circulating cell free mtDNA (ccf-mtDNA) in inflammation related neuromuscular diseases.

Neuromuscular diseases, mostly being among the rare genetic diseases, include a wide range of syndromes and diseases in which directly or indirectly affect skeletal muscle structure and function. Recent scientific research has focused on defining common mechanisms involved in the pathogenesis of rare diseases and identifying novel therapeutic targets. Inflammation is one of the prominent features of the majority of neuromuscular diseases. Studies carried out on different diseases have shown that circulating cell free mtDNA (ccf-mtDNA) is involved in the development of the innate immune response as a pro-inflammatory factor.

Absolute quantitation of the amount of ccf-mtDNA found in plasma of patients with (1) autoimmune neuromuscular diseases, (2) the hereditary neuromuscular diseases associated with muscle inflammation and (3) the hereditary neuromuscular diseases without muscle inflammation, was done by RT-qPCR and the results were analyzed in comparison with the healthy control samples.

In myasthenia gravis (MG), a statistically significant increase in the copy number of ccf-mtDNA by 5,6 fold (p=0,0119) were detected in the patients without any additional treatment compared to control, while there was a statistically significant 1,8 fold (p=0,0476) decrease in the copy number of ccf-mtDNA of the patients who received treatment compared to control. In FSHD and LGMD2B patients, there was no statistically significant difference in the ccf-mtDNA copy number. However, there was a statistically significant 2-fold increase (p=0,0017) in SMA patients.

The increase in ccf-mtDNA detected in neuromuscular diseases may be associated with systemic inflammation independent of local inflammation in skeletal muscle tissue.