The research, which analyzed data from 104 treated and 114 untreated patients, reveals that KYGEVVI—the first approved therapy for early-onset TK2d—dramatically alters disease trajectory. For patients who developed symptoms by age 12, treatment reduced the risk of death by 92% to 94%. Those receiving the medication lived an average of 29.2 years, compared to 14.4 years for untreated individuals. Beyond longevity, the therapy demonstrated functional efficacy, with 75% of patients in the early-onset subgroup regaining at least one motor milestone.

Contrasting these outcomes, the second study examined a natural history dataset of 257 untreated patients, illustrating the harsh reality of the disease. Among those with symptom onset by age 12, over half died at a median age of 1.9 years. The data highlights that the loss of motor milestones and the need for ventilatory or feeding support are common for those left without intervention. While diarrhea remains the most frequent side effect, researchers note it is generally manageable, marking a shift in the clinical landscape for a condition that previously offered only palliative care options.