The cardinal features of this syndrome are craniosynostosis and radial defects. However, a large number of variable defects such as imperforate or anteriorly placed anus, rectovaginal fistula, absent thumbs, polydactyly, and mental retardation may also be present. The radius may be completely absent or abnormally formed and occasionally the ulnar bone is involved as well. Some patients have a conductive hearing loss.