Individuals with GNB1-related disorder typically have some degree of developmental delay/intellectual disability, however, it is different from person to person. Some will be able to walk and talk independently, but others will require assistance.
Approximately, 50% of individuals with GNB1-related disorder have seizures. Most were described as being quite floppy as a baby (infantile hypotonia) and around 50% of them have findings on brain imaging. Some individuals with GNB1 changes have dystonia (involuntary muscle contractions).
Although many babies with GNB1 changes have difficulties with feeding and gaining weight after birth, most will eventually catch up on growth. Digestion problems (such as vomiting and constipation) can also occur. Some have vision and hearing issues. Other less common findings include heart issues, cleft palate, and genitourinary anomalies. Mastocytosis, a rare disease of the skin, has also been seen in some individuals with GNB1 changes.
Most of these features become present by early childhood. This is a genetic condition and is not related to environmental exposures or events during pregnancy or in early infant life.