Revisiting the recurrence risk of nonsyndromic cleft lip with or without cleft palate.

Sub-epithelial defects (i.e., discontinuities) of the superior orbicularis oris (OO) muscle appear to be a part of the phenotypic spectrum of cleft lip with or without cleft palate (CL ± P). Analysis of the OO phenotype as a clinical tool is hypothesized to improve familial recurrence risk estimates of CL ± P. Study subjects (n = 3,912) were drawn from 835 families. Occurrences of CL ± P were compared in families with and without members with an OO defect. Empiric recurrence risks were calculated for CL ± P and OO defects among first-degree relatives (FDRs). Risks were compared to published data and/or to other outcomes of this study using chi-square or Fisher's exact tests. In our cohort, the occurrence of CL ± P was significantly increased in families with OO defects versus those without (P < 0.01, OR = 1.74). The total FDR recurrence of isolated OO defects in this cohort is 16.4%; the sibling recurrence is 17.2%. The chance for one or more FDRs of a CL ± P proband to have an OO defect is 11.4%; or 14.7% for a sibling. Conversely, the chance for any FDR of an individual with an OO defect to have CL ± P is 7.3%; or for a sibling, 3.3%; similar to published recurrence risk estimates of nonsyndromic (NS) CL ± P. This study supports sub-epithelial OO muscle defects as being part of the CL ± P spectrum and suggests a modification to recurrence risk estimates of CL ± P by utilizing OO defect information.