A genetic disorder associated with variation(s) in the AP4 genes: AP4B1, AP4E1, AP4M1, and AP4S1. The phenotypes observed in individuals with genetic variants in these genes are often complex and include intellectual disability, spastic paraplegia, microcephaly, brain abnormalities, and seizures. [ http://www.ncbi.nlm.nih.gov/pubmed/30543385 http://www.ncbi.nlm.nih.gov/pubmed/32171285 http://www.ncbi.nlm.nih.gov/pubmed/29193663 http://www.ncbi.nlm.nih.gov/pubmed/29430868 https://clinicalgenome.org/affiliation/40006/ ]