PPP1R15B and Intellectual disability: Abdulkarim et al. (28) reported that after the R658C mutation in the PPP1R15B gene in two children, a conserved amino acid in the binding region of protein phosphatase-1 was affected, reducing PPP1R15B dephosphorylation and leading to β-cell apoptosis, small head disease, short stature, intellectual disability, and diabetes.