GRIN2B-Related Disorder.
Incidence
GRIN2B is not the name of a medical condition but rather is the name of the gene that is affected. When a disorder is traced back to a pathogenic variant in the GRIN2B gene, it is called a GRIN2B-related disorder or syndrome. In most children with GRIN2B-related disorders, the pathogenic GRIN2B variant occurred spontaneously (de novo) and was not inherited from either parent.
Clinical Characteristics
GRIN2B related syndrome is a genetic disorder that causes developmental delay and intellectual disability. Pathogenic variants (“mutationsâ€) in the GRIN2B gene cause a spectrum of neurodevelopmental disorders that can include childhood-onset epilepsy, developmental delays, movement disorders and features of autism spectrum disorder. The symptoms a child experiences and the severity of the disorder can vary widely. In many children, delays in achieving developmental milestones during infancy or early childhood may be the first indication of a GRIN2B-related disorder. In other children, seizures are the first sign of the condition. In most individuals with GRIN2B-related disorders, seizures begin in infancy or early childhood. However, the age of onset varies widely between individuals, ranging from shortly after birth to later in childhood. Many people with GRIN2B-related disorders may never develop epilepsy.
All children with GRIN2B-related disorders have some degree of developmental delay and cognitive impairment, which ranges in severity from mild to severe.
Epilepsy is a common feature of GRIN2B-related disorders, and is present in approximately half of children with this condition. Children with GRIN2B-related disorders may develop different types of seizures, which may be difficult to control with anti-seizure medications. Common seizure types may include: Infantile spasms, Focal impaired awareness seizures (seizures where children stop their usual behavior and become unaware), Focal motor seizures (abnormal movements or jerking of one part of the body), Generalized tonic-clonic seizures, also called grand mal seizures (in which the body, arms and legs extend, then contract and shake).
Many children with GRIN2B-related disorders also have: Decreased muscle tone (central hypotonia). Also increased muscle tone (spasticity) in the limbs. Movement disorders, including dystonia and chorea may be present. Behavior disorders, including aggression, hyperactivity or features of autism spectrum disorder. Cortical visual impairment may be seen. Small head size (microcephaly) as well as developmental brain malformations, such as polymicrogyria. However, there are no typical signs of a GRIN2B-related disorder that enable a diagnosis based on clinical features alone.
Precipitants
None
Provocation Tests
None
Diagnostic Procedures
Genetic testing for gene mutations is mandatory to make the diagnosis of this condition.