Doxecitine and Doxribtimine-Expanded Access

Inclusion Criteria: TK0113: * Pediatric and adult patients with a diagnosis of TK2d based on confirmed reportable variant(s) in the TK2 gene in countries where UCB has an affiliate/local safety officer Signs and symptoms compatible with TK2d disease * Risk of major disability or death resulting from TK2d * The patient must be willing to receive treatment with doxecitine and doxribtimine via this program, which includes signing an authorization form for sharing genetic test results, medical data and other related information with UCB, its third-party agents and health authorities * The patient/legal guardian or representative has given informed consent (and age-appropriate assent) to treatment prior to administering doxecitine and doxribtimine in a manner consistent with all national requirements. This also includes consent for the transmission of a copy of the anonymized data, such as serious adverse event (SAE) and pregnancy reports (in compliance with local regulatory authority requirements) to UCB third-party agents where allowable by local regulations and to the country regulatory authority as required. * The patient does not qualify for or is unable to participate in a UCB sponsored ongoing clinical trial evaluating doxecitine and doxribtimine. TK0115: * Diagnosis of TK2d based on confirmed reportable variant(s) in the TK2 gene * Age of TK2d symptom onset ≤ 12 years * The patient or care provider must be willing to receive treatment with doxecitine and doxribtimine v…