Families

Mutations in the GRIA, GRIA2, GRIA3, and GRIA4 gene cause a rare disorder characterized by a general developmental delay. This is apparent from infancy or early childhood, resulting in variable intellectual disability ranging from mild impairment with an ability to attend special schools to profound impairment with absent speech and none to limited social skills. Although the majority of patients eventually learn to walk, most are late to reach this milestone and have an unsteady gate. Some experience periods where the development regresses or stands still. Many have behavioral difficulties including autistic features, reduced attention span, aggression towards self and others, anxiety and hypersensitivity to input. While some patients are very flacid (loss of body tone) while other affected infants show irritability, stiffness, and hypertonia early in life, which progresses to spasticity and impaired walking later in life. Some patients may develop epileptic seizures of variable severity early in life.

Not all individuals with a mutation in the GRIA1-4 genes have these features.

Both males and females can be affected by mutations in these four genes. In most circumstances the mutation is not inherited from any of the parents. GRIA3 is located at the X chromosome and some affected males may have inherited a mutations from an unaffected mother who acts as a carrier of the gene.