In Pierre Robin sequence with cleft palate, micrognathia, and glossoptosis, a 50% prevalence of hypodontia, excluding the third molars, has been reported. Hypodontia in the mandible is more frequent in Pierre Robin patients than in that of the cleft patients (Ranta, 1986).
Even higher prevalence of hypodontia (69%) has been shown in patients with the autosomal dominant Van der Woude syndrome associated with cleft lip and/or palate and pits of the lower lip. Mutations in the IRF6 (interferon regulatory factor 6) gene in has been reported 1q32-41 in families with van der Woude or popliteal pterygium syndromes (Kondo et al, 2002). The mutations included missense, nonsense and indel-mutations. The authors suggested that loss-of-function mutations typically cause Van der Woude syndrome whereas missense mutations of the residues that directly interact with DNA cause a more severe phenotype of popliteal pterygium syndrome through a dominant-negative mechanism. Genetic heterogeneity in Van der Woude syndrome has been suggested and linkage to another region of chromosome 1 has been reported (Koillinen et al, 2001).
Text partially adapted from Sirpa Arte: Phenotypic and genotypic features of familial hypodontia. Dissertation, Institute of Dentistry, University of Helsinki, Finland, 2001.
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