ABCC8 and Phelan-McDermid syndrome: In the case of SUR, the cause may be dysregulation of glutamatergic neurotransmission: Phelan-McDermid Syndrome produces disruption in the SHANK3 gene, which encodes a scaffolding protein in glutamatergic synapses, and produces a specific autistic phenotype in which SUR is considerably more prevalent than in idiopathic autism (Tavassoli et al., 2021).