Mitochondrial Diseases
There are many types of diseases affecting mitochondria, each characterized by progressively worsening symptoms and involving multiple organs or organ systems.5 They are often fatal. While rare, mitochondrial disease may actually be more common than some may think.1,6
How TK2d impacts the body
In normally functioning cells, the TK2 enzyme aids in the phosphorylation of deoxythymidine and deoxycytidine, which is a critical step in the production of mitochondrial DNA (mtDNA). mtDNA is needed by mitochondria to produce energy for the cells and the body.7-9
TK2d is the result of a mutated thymidine kinase 2 (TK2) gene, which encodes for the TK2 enzyme. The genetic mutation disrupts mtDNA synthesis, which results in an energy deficit that causes progressive muscle weakness/muscular degeneration and multisystem involvement.7,9
When to consider genetic testing
The complex presentation is a barrier to diagnosis, often resulting in misdiagnosis or delayed diagnosis.5 However, advancements in genetic testing have made diagnosing mitochondrial diseases such as TK2d easier. If you see red-flag symptoms of mitochondrial diseases, consider conducting a genetic test to help shorten the diagnostic journey.11,12
Reduced energy/fatigue
Muscle weakness
Difficulty swallowing or walking
Neurological symptoms (eg, epilepsy, ataxia, hearing loss)
In infants: hypotonia, weakness, failure to thrive, and metabolic acidosis (especially lactic acidosis)
TK2d is a rare, inherited, and often fatal disease8,13
TK2d is classified as mitochondrial DNA depletion/deletion syndrome, a category of mitochondrial disease.13
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