Early genetic diagnosis of thymidine kinase 2 deficiency (TK2d) can quickly clarify a devastating condition and help families make informed medical and ethical decisions, according to a rare neonatal case published recently in the Indian Journal of Case Reports.
“Timely diagnosis allowed the family to make informed decisions and provided critical information for future pregnancy planning,” explained the authors of this case report.
In this case, a 25-year-old pregnant woman had a largely normal early pregnancy. However, at 32 weeks and four days, an ultrasound showed fetal growth restriction, mild excess amniotic fluid and concerning findings such as an absent stomach bubble and scalp swelling. These findings initially raised suspicion for structural abnormalities.
Read more about testing and diagnosis for TK2d
The infant, delivered by emergency cesarean section due to fetal distress, showed signs of distress immediately after birth. Apgar scores (a measure of a newborn’s health) were 3 and 5 at one and five minutes. The newborn had poor muscle tone, appeared limp and developed respiratory failure within the first day of life, requiring mechanical ventilation. Despite intensive care, symptoms persisted, raising concern for an underlying neuromuscular or metabolic disorder like TK2d.
Whole exome sequencing confirmed a homozygous mutation in the TK2 gene, establishing the diagnosis of TK2d. This form follows an autosomal recessive inheritance pattern, meaning both parents are carriers and each pregnancy carries a 25% risk of recurrence. Given the severe and progressive nature of infantile TK2d, clinicians provided detailed counseling about prognosis, expected disease course and quality of life. After these discussions, the family decided to seek care at an advanced center.
For patients and families, early diagnosis of TK2d can avoid prolonged uncertainty and unnecessary interventions. It enables clearer decision-making about treatment options and supports planning for future pregnancies through genetic counseling and testing. While emerging therapies such as nucleoside replacement show promise, outcomes remain variable, making early identification of TK2d critical for both care and family guidance.
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