Late-onset thymidine kinase 2 deficiency: a review of 18 cases

TK2 gene encodes for mitochondrial thymidine kinase, which phosphorylates the pyrimidine nucleosides thymidine and deoxycytidine. Recessive mutations in the TK2 gene are responsible for the ‘myopathic form’ of the mitochondrial depletion/multiple deletions syndrome, with a wide spectrum of severity. We describe 18 patients with mitochondrial myopathy due to mutations in the TK2 gene with absence of clinical symptoms until the age of 12. The mean...