Mixed clefting type in Rapp-Hodgkin syndrome.

Mixed clefting type (MCT) is the rare occurrence of cleft lip, with or without cleft palate, and cleft palate alone in the same pedigree. Here we present a family with Rapp-Hodgkin syndrome (RHS) that manifests MCT, and use this rare finding to suggest that RHS may be related not only to phenotypically similar syndromes, but seemingly dissimilar ones as well. RHS has obvious phenotypic overlap with other ectodermal dysplasia-clefting syndromes (EDCS), such as ectrodactyly-ectodermal dysplasia-clefting syndrome (EEC) and ankyloblepharon-ectodermal dysplasia-clefting syndrome (AEC), all of which show MCT. MCT is also found in the allelic disorders van der Woude syndrome (VDW) and popliteal-pterygium syndrome (PPS). Therefore, while VDW and PPS have little clinical overlap with the EDCS, the common finding of MCT may indicate closer relationships at the developmental or genetic level.