Craniofacial characteristics of Proteus syndrome: two modes of abnormal growth.

The dysmorphic growth patterns of the craniofacial skeleton are summarized in five patients with the Proteus syndrome. Two different modes of abnormal growth are present. One mode involves focal overgrowth of membrane bones, producing multiple hyperostoses which result in progressive craniofacial disfigurement and asymmetry. The second mode involves overgrowth of cartilage in the condyle, resulting in dentofacial asymmetry. The phenotype of the craniofacial skeleton results from both processes. In terms of appearance, the mode involving hyperostosis seems more dramatic in most cases than the mode involving cartilage.