Intragenic loss of function variants cause a relatively homogeneous phenotype consisting of severe DD/ID with no walking, absent or very limited language skills and dystonia or chorea. Microcephaly and increased muscle tone/pyramidal signs are frequently observed. Seizures are present in few individuals. On rare occasions, an apparently progressive course is reported. Brain MRI frequently shows abnormal white matter. Sensorineural hearing loss is a frequent feature. liver enzyme elevation, either permanently or intermittently, is seen, sometimes during febrile episodes.
Patients with missense variants have a somewhat milder phenotype although clinical observations were made on a very small number of patients.
Non syndromic hearing loss can be observed as an isolated feature in carrier females. Intellectual disability (usually mild) can be present.
BCAP31