grin2b-related neurodevelopmental disorder grin2b-related neurodevelopmental disorder grin2b-related neurodevelopmental disorder is a rare neurodevelopmental disorder which is characterized by developmental delays and intellectual disabilities of variable degrees, muscle tone anomalies, feeding difficulties, and behavioral problems. grin2b-related neurodevelopmental disorderother namesgrim2b-associated disorderspecialtymedical genetics, pediatry, neurologysymptomsmainly developmental delays, intellectual disabilities, craniofacial dysmorphisms, behavioural problems and muscle tone anomaliescomplicationslearning disability, communication delay, social ineptionusual onsetbirthdurationlifelongcausesgenetic mutationdiagnostic methodgenetic testing and physical examinationpreventionnoneprognosismediumfrequencyrare, only 100 cases have been described in medical literaturedeaths- signs and symptoms the following list comprises most of the symptoms people with grin2b show: intellectual disability (mild to severe) developmental delay (mild to severe) hypotonia epilepsy autism spectrum disorder autistic-like behavior microcephaly hyperactivity stereotypy spasticity feeding difficulties less common symptoms include: visual impairment dystonia dyskinesia other choreiform movement disorder causes this condition is caused by mutations in the grin2b gene, located in chromosome 12. this gene makes instructions into how to make a protein called glun2b, a type of nmda receptor, which is found in brain neurons during ante-natal brain development. it is involved in correct brain development and function, regulating memory, synaptic plasticity and the ability of learning. epidemiology around 100 cases have been described in medical literature.