Pettigrew Syndrome, also known as mrxs21, is related to dandy-walker syndrome and hydrocephalus, and has symptoms including muscle spasticity, seizures and gait ataxia. An important gene associated with Pettigrew Syndrome is AP1S2 (Adaptor Related Protein Complex 1 Subunit Sigma 2), and among its related pathways/superpathways are Class I MHC mediated antigen processing and presentation and HIV Life Cycle. Affiliated tissues include brain and eye, and related phenotypes are macrocephaly and gait disturbance