Clinical Characteristics

The following description of the broad clinical spectrum is based on 20 individuals reported in Chen et al., Genet Med. 2016.


Growth parameters

Usually normal height, weight and head circumference.


Neurological features

Individuals with BBSOAS have developmental delay and intellectual disability. However, low normal IQ has been described. Muscle weakness (hypotonia) in the first period is common. Difficulties with controlling the mouth muscles, leading to e.g. feeding problems or speech problems are present in about half of the cases. Seizures are variable present, ranging from no epilepsy to infantile spasm to onset of seizures at the age of 18 years.

On brain imaging a thin corpus callosum can be seen. The corpus callosum is the connection between the two parts (hemispheres) of the brain.


Neuropsychological disorders

Behavioral problems are present in about half of the individuals with BBSOAS, including autism spectrum disorder and/or attention deficit hyperactivity disorder. Repetitive behavior is also observed.


Visual and hearing impairments

Many individuals have vision impairment, due to a thin or abnormal optic nerve (the connection between the eye and the brain) and/or cerebral visual impairment (CVI). In CVI the eye functions normal, but the interpretation of the visual information in the brain is disturbed.

Hearing impairment can also be present in persons with BSSOAS.