together,
we have the power to take onTK2d
If you're just learning about TK2d, you may be feeling overwhelmed and unsure of the future. You probably have lots of questions, and genetic testing may give you some answers.
Genetic testing is the most direct way to find out if you have TK2d. Early genetic testing can confirm a diagnosis and help patients seek the care they need.
If you're just learning about TK2d, you may be feeling overwhelmed and unsure of the future. You probably have lots of questions, and genetic testing may give you some ansers.
Genetic testing is the most direct way to find out if you have TK2d. Early genetic testing can confirm a diagnosis and help patients seek the care they need.
What is TK2d?
Thymidine kinase 2 deficiency (TK2d) is a rare genetic mitochondrial disease
TK2d is a genetic mitochondrial disease that can have a serious impact on a person's health and quality of life. To best understand TK2d, there are some things about the body that you need to know first.
Mitochondria and ATP
DNA and mtDNA
Mitochondrial disorders
Understanding TK2d
TK2d is a myopathic form of mitochondrial disease, meaning it affects muscles. It is also a type of mitochondrial disease called mtDNA depletion syndrome.
Thymidine kinase 2 (TK2) is an enzyme that helps make and maintain your mtDNA. When you have a healthy and normal amount of mtDNA, the mitochondria are able to create and provide energy for your body and its functions.
TK2d is caused by mutations in the TK2 gene, which decrease the enzyme activity that helps make and repair your mtDNA. Because there isn’t enough healthy mtDNA, the mitochondria cannot work the way they should. This means muscles don’t have enough energy and cannot function properly. This can lead to weakness in many muscle groups.
quick facts
- TK2d was first described in children in 2001
- In 2013, improved genetic testing led to the discovery of an adult-onset form of TK2d
Because the genetic testing that finds TK2d is so new, and there are many other diseases with symptoms like those of TK2d, it is thought that there are many more people with TK2d who have not been properly diagnosed.
What are the symptoms of TK2d?
TK2d has progressively taken away my physical strength, my ability to eat, swallow, and breathe.
Doreen
lives with TK2d
TK2d is defined by severe muscle weakness (called myopathy) and can affect life in a range of ways. Many patients lose the ability to walk, eat, and breathe independently. Tragically, it is also often life-threatening.
Because TK2d is a disease with many symptoms, diagnosing TK2d can be a long journey. It can take multiple visits to health care providers to get a confirmed TK2d diagnosis.
However, if you suspect TK2d, genetic testing is the most direct path to a diagnosis.
TK2d causes a spectrum of symptoms that can affect people of all ages
Symptoms can progress slowly or quickly, depending on the patient and age of onset. Generally, the earlier in life symptoms start, the more severe they are and the quicker they progress.
Symptoms of
Early onset
TK2d
Young children often have a healthy birth and reach early developmental milestones. Shortly after, they may experience:
Young children often have a healthy birth and reach early developmental milestones. Shortly after, they may experience:
(trouble breathing)
(hypotonia, also called floppy baby syndrome)
(like crawling, walking, balancing, and grabbing)
Symptoms of
Late onset
TK2d
Teens and adults often have symptoms that do not progress as quickly as early onset TK2d, including:
Teens and adults often have symptoms that do not progress as quickly as early onset TK2d, including:
Getting a diagnosis
If you or a loved one has several of the symptoms listed above and you suspect TK2d, there are no-cost genetic testing options to help with a diagnosis. And with each new diagnosis, we can discover more about TK2d.
What causes TK2d?
Symptoms of TK2d begin to appear early in life for many patients, but TK2d can sometimes develop in teens and adults, too.
TK2d is an inherited disease caused by a genetic mutation in the TK2 gene. Both the mother and father (called “carriers”) must have a copy of the altered TK2 gene for a child to get TK2d. This is called an autosomal recessive inheritance pattern.
When both parents are carriers of the TK2 gene, each child will have a 25% chance of having TK2d, a 50% chance of being an unaffected carrier, and a 25% chance of not having TK2d and not being a carrier.
The mother and father who pass on TK2d will usually not have any signs or symptoms of the disease. That is one reason why getting a diagnosis can be hard for someone who inherits TK2d.
If you or a loved one has been diagnosed with TK2d, you should also talk to your doctor about how to learn if siblings or other family members may be carriers.
These are the possibilities with two carrier parents:
25%
Chance of having TK2d
50%
Chance of being an unaffected carrier of a single mutated TK2 gene
25%
Chance of not having TK2d and not being a carrierHow is TK2d managed?
While TK2d can often have serious or even life-threatening consequences, doctors can help manage the symptoms of TK2d to try to limit its impact. They may use medical equipment and therapies such as:
- Respiratory support/therapy
- Feeding tubes
- Wheelchairs
- Physical therapy
- Nutraceuticals (sometimes called a "mito cocktail")
Caring for someone with TK2d usually involves a multidisciplinary team that includes a physical therapist to help keep muscles functioning and other specialists as needed (e.g., a pulmonologist to manage breathing problems). A multidisciplinary team may include:
- Neurologists
- Pulmonologists
- Metabolic specialists
- Gastroenterologists
- Physical therapists
- Speech therapists
- Clinical genetics
- Genetic counselors
While there are no FDA-approved therapies to treat TK2d, we continue to learn more about the disease and potential treatments
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