Intellectual Developmental Disorder, X-Linked, Syndromic, Billuart Type, also known as x-linked intellectual disability-cerebellar hypoplasia syndrome, is related to ophn1 syndrome and deafness, dystonia, and cerebral hypomyelination. An important gene associated with Intellectual Developmental Disorder, X-Linked, Syndromic, Billuart Type is OPHN1 (Oligophrenin 1), and among its related pathways/superpathways are Metabolism of cofactors and Mitochondrial iron-sulfur cluster biogenesis. Affiliated tissues include brain and eye, and related phenotypes are intellectual disability and global developmental delay