GRIN2B and Delayed speech and language development: Some mutations in GRIN1 were associated with intellectual disability, behavioral abnormalities, and stereotypical movements 61, while others in GRIN2A correlated with a spectrum of neurodevelopmental disorders with speech delay, apraxia and EP 62; similarly, some mutations in GRIN2B were associated with neurodevelopmental disorders characterized by mild to profound developmental delay/intellectual disability, often with EP and ASD behaviors 63.