A Study of Cephalometric Features in Cleft Lip- Cleft Palate Families I: Phenotypic Heterogeneity and Genetic Predisposition in Parents of Sporadic Cases

Abstract

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 pheno-typic 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 KEY WORDS: cleft lip, cleft palate, sporadic cleft lip and palate, cephalometrics, cluster analysis A recurring theme in the study of oral clefts is that non-cleft relatives of affected individuals may display unusual facial features that distinguish them from the general population. Central to most of these studies is the premise that such unique features reflect the expression of genetic susceptibility to clefting. Thus, Trasler (1968), citing experimental evidence from mice, suggested that the shape of the embryonic face could be a predisposing factor to clefting. Fraser and Pashayan (1970) also theorized that such predis-posing factors should be evident in the human face, and they demonstrated that parents of individuals with clefts had a suite of facial features that distinguished them from a normal control group. Coccaro et al (1972), Kurisu et a1 (1974), Nakasima and Ichinose (1983), and Prochazkova and Tolarova (1986) expanded on these earlier results and in each case demonstrated that noncleft parents of children with clefts had facial features that differed quantitatively Richard E. Ward is Assistant Professor,