Thymidine kinase 2 deficiency (TK2d) is a rare genetic disorder that affects voluntary muscle function, causing muscle weakness that leads to trouble breathing, swallowing and moving independently. While there is no cure, early diagnosis can open the door to earlier treatment and help delay progression of the disease.
What is TK2d?
If you’re searching for a diagnosis and a doctor mentioned TK2d as a possibility, you’re not alone if you’ve never heard of the disease: It was only identified in 2001, and is thought to affect between 600 and 2,700 people in the United States.
TK2d is a rare genetic mitochondrial disorder that is caused by mutations in the Tk2 gene, a gene important for mitochondria to function correctly. Often called the “powerhouse” of the cell, mitochondria convert oxygen and other substances into energy. Without this energy, patients with TK2d experience muscle weakness that progresses over time.
There is still much to be learnt about the disorder, and clinical research is ongoing.
What impact does early diagnosis have on health in TK2d?
In TK2d, early diagnosis means early treatment, and better long-term health.
The most common cause of death in people with TK2d is respiratory failure: as muscle weakness progresses, the muscles that control breathing become increasingly affected. Patients eventually aren’t able to breathe on their own anymore and will need mechanical ventilation.
Treatment can help slow down the progression of TK2d. In patients diagnosed at 12 years and younger, a new FDA-approved medical treatment called Kygevvi (doxecitine and doxribtimine powder) that targets the root cause of the disease has been shown to delay progression of symptoms and prolong survival.
Beyond this therapy, early care from a multidisciplinary care team can also improve life with TK2d. Patients will likely work with a physical therapist to maintain muscle strength and function, a respiratory therapist to build their breathing muscles and a speech therapist to manage swallowing problems.
Learn more about TK2d treatment and care
How is TK2d diagnosed?
If TK2d is suspected based on patient symptoms and medical history, the only way to confirm it is via laboratory tests — specifically genetic testing for variants in the TK2d gene.
TK2d is challenging to diagnose and is often mistaken for one of a range of neuromuscular disorders. As a rare mitochondrial disease, there is a lack of awareness amongst doctors about the disease. Patients often experience long delays before receiving the correct diagnosis and care.
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