A study of cephalometric features in cleft lip-cleft palate families. I: Phenotypic heterogeneity and genetic predisposition in parents of sporadic cases.

Several previous studies have indicated that unaffected parents of children with nonsyndromic cleft lip and palate show unusual craniofacial features. This study reexamines this question by applying multivariate cluster analysis to lateral cephalometric head plates from 82 individuals who are parents of sporadic cases of cleft lip with or without cleft palate (CL/P). Considerable phenotypic heterogeneity was present within the sample. Three major groupings were defined. Two of these groups showed cephalometric similarities to individuals with overt clefts, while the third showed a generalized concordance to published norms. In almost every case only one member of each parental pair showed the cleft related cephalometric phenotype, suggesting the possibility of a substantial genetic component in many cases of sporadic CL/P. However, there were several cases in which neither parent showed the phenotypic traits. Such cases may have a different etiology or a greater environmental component.