TRAPPC9 gene mutations have been linked recently to autosomal recessive mental retardation 13 (MRT13; MIM#613192) with only eight families reported world-wide.
Mutations in the TRAPP complex subunit 2 (TRAPPC2) cause X-linked spondyloepiphyseal dysplasia tarda, while mutations in the TRAPP complex subunit 9 (TRAPPC9) cause postnatal mental retardation with microcephaly.