MBD5 (Methyl-CpG-binding domain 5) is a critical gene for normal development. Microdeletions of 2q23.1 disrupting MBD5 and loss of function mutations of MBD5 cause MBD5-Associated Neurodevelopmental disorders (MAND).MBD5-associated neurodevelopmental disorder (MAND) is an umbrella term that describes a group of disorders, 2q23.1 deletion syndrome, 2q23.1 duplication syndrome, and MBD5 variants, that affect the function of methyl-binding domain 5 (MBD5) and share a common set of neurodevelopmental, cognitive, and behavioral impairments. Methyl-CpG-binding domain 5 (MBD5)-associated neurodevelopmental disorder caused by 2q23.1 or MBD5-specific mutation has been recently identified as a genetic disorder associated with autism spectrum disorders. MBD5 haploinsufficiency is a neurodevelopmental disorder characterized by global developmental delay/intellectual disability (ID), severe speech impairment, seizures, sleep disturbances, and abnormal behaviors.