Ultrasonographic detection of orbicularis oris defects in first degree relatives of isolated cleft lip patients

The phenotypic variability of non-syndromic cleft lip (CL) is broad. We dem onstrate that the prevalence of orbicularis oris (OO) muscle anomalies, det ectable only by ultrasound, is higher in first-degree relatives of individu als with overt CL than in the general population. These findings suggest th at occult OO defects may be part of the spectrum of the CL phenotype, that offspring of individuals with such defects are at an increased risk to deve lop overt CL, and that ultrasound may be a useful tool in future population studies designed to identify CL susceptibility genes. Am. J, Med, Genet. 9 0: 155-161, 2000, (C) 2000 Wiley-Liss, Inc.