DDB1 and Cognitive impairment: The five different de novo variants in the monofunctional DNA-alkylating methyl methanesulfonate (MMS1) domain of DDB1 have been previously identified in eight unrelated pediatric patients primarily exhibiting symptoms such as hypotonia, developmental delay, cognitive impairment, obesity, skeletal abnormalities, and dysmorphic features (OMIM: 619426) with an autosomal dominant inheritance.