Aside from previously discussed genes, additional monogenic causes, with or without ASD or autistic features, should be considered: adenylosuccinate lyase deficiency [85,86], GABRA1 (γ-aminobutyric acid type A receptor alpha1 subunit) [87], KCNQ3 (Potassium Voltage-Gated Channel Subfamily Q Member 3) [88], PCDH19 (Protocadherin 19) [89], SETD5 (SET Domain Containing 5) and TBL1XR1 (TBL1X Receptor 1) [90], AP3B2 (Adaptor-Related Protein Complex 3 β 2 Subunit) [91], CACNA1B (Calcium Voltage-Gated Channel Subunit Alpha1 B) [92], GNAO1 [93] and SZT2 (seizure threshold 2) related disorders [94]. Here, TBL1XR1 is linked to hyperinsulinemic hypoglycemia, familial, 4.