Clinical findings
Developmental delay (DD) is the most common clinical feature but varies from mild to severe among affected individuals. Many children with SLC6A1-NDD come to medical attention because of low muscle tone and delayed motor and language milestones within the first year of life.
Language development is often more delayed than motor development.
Intellectual disability (ID). Approximately one third of individuals will have ID; severity varies from mild to severe. Many of those who do not meet the criteria for ID will have a specific learning disorder such as dyslexia.
Other manifestations. Approximately one third of individuals have autism spectrum disorder, and 10%-20% have attention-deficit/hyperactivity disorder (ADHD).
Epilepsy. Several seizure type have been reported in individuals with SLC6A1-NDD:
Age of onset is typically early childhood.
Movement disorders. Approximately half of individuals with SLC6A1-NDD have abnormal movements.
Behavioral issues are common in individuals with SLC6A1-NDD and likely have a significant contribution to the burden of disease.
Prognosis
Life expectancy is not reduced. Seizure may be ongoing despite anti-seizure medications. Some individuals are incapable of independent living.
SLC6A1