TK2d Basics

There is currently no cure for thymidine kinase 2 deficiency (TK2d).

Kygevvi (doxecitine and doxribtimine) powder became the first drug approved by the U.S. Food and Drug Administration in November 2025 to treat thymidine kinase 2 deficiency (TK2d) in patients who showed symptoms when they were 12 years old or younger.

Apart from this therapeutic approach and a combination approach of gene therapy and nucleoside therapy currently being studied, the main treatment and care options for TK2d involve supportive treatments that focus on alleviating the symptoms of the disease and improving quality of life. These include ventilation and feeding support, rehabilitation, physical therapy and lifestyle and wellness strategies.

Supportive treatments

The main symptom of TK2d is progressive muscle weakness that can also affect the muscles used for breathing and swallowing. In fact, respiratory failure is the most common cause of death among patients with the disease.

Ventilatory support may be needed to ensure patients can breathe. This can either be non-invasive or invasive.

In non-invasive ventilation, air is delivered to the lungs via a sealed mask that is placed over the mouth, nose or whole face.

In invasive ventilation, on the other hand, air is delivered to the lungs through a tube that is inserted into the windpipe via the mouth or the nose.

To support feeding in TK2d and reduce the risk of aspiration, i.e., food mistakenly going down the windpipe and causing choking, a nasogastric or gastrostomy tube may be needed. This can not only make sure patients receive all the nutrients that they need, but it can also abolish the risk of aspiration. 

A nasogastric tube consists of a thin plastic tube that is inserted through a nostril and goes from the back of the throat down to the stomach. 

A gastrostomy tube is a device that is surgically placed onto the abdomen and provides direct access to the stomach. 

In both cases, food, liquids or medication can be directly delivered to the stomach.

Rehabilitation and physical therapy

Physical therapy can be used to help manage muscle weakness affecting patients with TK2d. It can also help prevent joint contractures, increase range of motion and guide patients on the use of assistive devices like a wheelchair for mobility.

Chest physiotherapy can help manage reduced lung function, clear mucus and reduce the risk of lung infections.

Lifestyle and wellness strategies

Although there are no specific guidelines in place for treating TK2d, dietary guidelines for mitochondrial disease may also be applicable.

These include consuming four to six small meals each day that include both a complex carbohydrate and a protein such as eggs, milk, yogurt, soy, fish, meat, nuts, beans and cheese. It also includes avoiding caffeine and staying well hydrated.

Dietary supplements such as Coenzyme Q₁₀, Vitamin B2 and alpha lipoic acid are recommended by the Mitochondrial Medicine Society for patients with mitochondrial disease. These may also be beneficial for patients with TK2d, but you should always contact a healthcare professional before taking or giving your child any supplements.

It is also important that caregivers of patients with TK2d use wellness strategies to ensure they do not burn out while providing care for their patients. These may include creating time for themselves, practicing daily self-care moments and getting enough sleep.