Individuals with STAG1-related neurodevelopmental disorder most often present with global developmental delay and intellectual disability ranging from mild to moderate severity. Speech delay is a very common feature, with expressive language usually more affected than receptive language.
Hypotonia in infancy is frequent and contributes to delayed motor milestones; some individuals show mild coordination difficulties or an unsteady gait. Behavioural abnormalities are common, including autism spectrum disorder or autistic traits, attention difficulties, and anxiety.
A proportion of individuals develop epilepsy, with variable seizure types; others may have EEG abnormalities without overt seizures. Brain MRI is frequently normal, but some patients show nonspecific findings such as a thin corpus callosum or mild white-matter changes.
Facial features tend to be mild and non-specific, but recurrent findings include a broad or prominent forehead, deep-set eyes, and a wide or full mouth. Growth is generally normal, though occasional cases of microcephaly or macrocephaly have been reported.
Additional features described in a subset of patients include:
• Vision or hearing problems, such as refractive errors, strabismus, or mild hearing impairment
• Musculoskeletal anomalies, including scoliosis, vertebral anomalies, joint laxity
• Congenital anomalies, such as congenital heart defects or cryptorchidism in males
STAG1