Helping families and clinicians connect the signs that may point to TK2d

A diagnosis often begins with subtle signs that something is not quite right. For families with thymidine kinase 2 deficiency (TK2d), finding an explanation for those first concerns can take time. TK2d is ultra-rare and can present differently from person to person, with symptoms that can overlap with other neuromuscular or mitochondrial diseases. Progressive muscle weakness may affect walking, eating and breathing, making it difficult to differentiate TK2d versus other conditions in clinical practice.

As we mark TK2d Awareness Day and World Mitochondrial Disease Week, we have been thinking about what it really takes to help families find answers sooner, though we come to that question from different places. Whether the perspective is personal as a caregiver and advocate or clinical as a leader in rare disease therapeutic development, we believe earlier recognition starts with listening to patients and caregivers as much as it does with science.

Recognizing possible signs sooner

The first signs of TK2d may not form a clear clinical pattern. What we hear from the community is how hard it can be to explain small changes, like pausing more often when walking, finding the stairs more difficult to climb or noticing that everyday activities take more effort than they used to, which create a growing sense that something is wrong, often leading to appointments where each answer raises another question. These experiences are frequent and can provide important clues alongside the clinical signs that healthcare professionals (HCPs) see in front of them.

We see this uncertainty from a clinical perspective also, where earlier recognition can help turn a muddled path into a clearer direction and can help healthcare professionals ask the next important question. Genetic testing can be an important turning point to achieving a diagnosis, helping put a name to what families have been living through by identifying disease-causing variants in the TK2 gene.

Together, they point to the same need to bring TK2d into the conversation earlier when symptoms suggest a mitochondrial or neuromuscular disorder. People living with TK2d, caregivers, advocacy groups, clinicians, researchers and industry partners all have a role in shortening the path to diagnosis and ensuring TK2d is considered when the clinical pattern fits.

Listening to what families carry into the consultation

A consultation can only capture a snapshot of what someone is experiencing. Families, however, see how symptoms show up and change in everyday life, whether it’s changes in mobility or energy or the impact on activities that may once have felt routine. Through our conversations with rare disease communities, we have seen how important it is to acknowledge these experiences as valuable context to enhance the clinical picture.

Beyond the progressive physical impact, TK2d has a significant impact on people’s mood, social and working lives, leaving them to feel disconnected. Furthermore, the emotional weight caused by waiting for an answer adds to the complexity and challenge of the journey. A name can help families make sense of symptoms and have more meaningful conversations with healthcare teams. These discussions can also help HCPs as, when they understand the medical features and lived experience behind them, they are better placed to recognize when testing may be appropriate and how to provide support.

This is especially important in ultra-rare diseases, where diagnosis is inherently challenging. Clinician education is important, coupling clinical features and triggers that prompt further evaluation and genetic testing alongside the real-world experience and voices of those living with the disease. While unrealistic to assume that all healthcare providers have in-depth awareness of all ultra-rare and rare conditions, clinical awareness of the signs and symptoms associated with rare neuromuscular disorders helps to raise suspicion and accelerates the path to a confirmed genetic diagnosis.

Connecting awareness with action

Bringing TK2d into the diagnostic conversation is more than identifying a rare condition. It is about seeing the people behind the symptoms and helping HCPs recognize when it may be time to go deeper.

When lived experience and clinical knowledge come together, awareness becomes more useful for everyone involved. It can help families feel heard, and clinicians consider the right next steps sooner, moving people closer to the answers they need.