New blood tests, wearable devices and advanced brain scans are improving the ability to diagnose and monitor primary mitochondrial diseases, according to a recent review published in the Journal of Neurology.
Primary mitochondrial diseases, including thymidine kinase 2 deficiency (TK2d), affect roughly 1 in 4,300 people and occur when faulty genes cause mitochondria, the “power plants” of the cells, to stop working properly.
To check whether you have a primary mitochondrial disease, how severe it is and whether a treatment is working, doctors measure certain biological markers, or “biomarkers,” often by doing a muscle biopsy (where a small sample of muscle tissue is removed, via needle or small incision, to be examined under a microscope).
Researchers are now looking for less invasive ways to measure disease severity. Two blood proteins, FGF21 and GDF15, have emerged as the most promising markers so far. GDF15 is particularly useful in TK2d, where it rises with disease severity and falls when treatment is working. Neurofilament light chain, a protein already used to monitor neurodegenerative diseases like multiple sclerosis, is also showing promise in mitochondrial disease patients.
Wearable fitness sensors offer another avenue for tracking patients in daily life. Studies show that step counts and gait measurements correlate with how severely patients are affected, and these tools could eventually help researchers to measure the efficacy of a treatment in clinical trials.
Brain and muscle scanning technologies are also advancing. For example, specialised MRI techniques can map and visualize areas where cellular energy production is failing.
Read more about TK2d testing and diagnosis
The authors of the review caution that no single test works well enough on its own to diagnose and monitor mitochondrial diseases. “At this stage, rather than replacing traditional measures, these biomarkers should be viewed as adjunct options that can refine diagnostic confidence and support clinical monitoring,” they said. “They are likely to play an increasingly important role in patient stratification and in providing objective readouts of disease activity and treatment response, particularly in clinical trials.”
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