A nucleoside-based treatment to improve respiratory impairment in TK2-deficient myopathy ?

Thymidin kinase 2-deficient myopathy (TK2-deficient myopathy) is a rare mitochondrial disease of varying severity. However, it causes very frequently a weakness of the diaphragm, the reason why half of patients have the first medical consultation, and has a poor prognosis. A nucleoside-based treatment allowed functional improvement in preclinical and compassionate use programme in a small group of patients with TK2-deficient myopathy. 

For the first time, a Spanish team has studied the effects of this treatment based on nucleosides (deoxythymidine and deoxycytidine) orally on the respiratory function of 6 persons with TK2-deficient myopathy for an average of 30 months (8 to 48 months). The median age of onset was 35.8 years. All of them presented a severe respiratory failure before the beginning of treatment and 4 were on non-invasive mechanical ventilation (NIV) at home. 

The results of this study published in November 2020 showed that respiratory function was improved or stabilized with: 

  • a statistically significant improvement in vital capacity (mainly during the first year of treatment), 
  • a non-significant improvement in the strength of the inspiratory muscles (on the MIP and the SNIP) .

At the end of the follow-up, the 6 persons were all on NIV but without an increase in their ventilatory support needs. However, further large-scale studies are needed to confirm these results. 


Deoxynucleoside therapy for respiratory involvement in adult patients with thymidine kinase 2-deficient myopathy. A Hernandez-Voth, J Sayas Catalan, M Corral Blanco et al. BMJ Open Respir Res. 2020 Nov. (1):e000774.