On the pathogenesis of cleft palate in the Pierre Robin syndrome.

In a series of Pierre Robin syndrome (PRS) and isolated cleft palate patients (ICP) both U- and V-formed clefts were observed with equal frequency, but the PRS clefts were in average slightly wider. There were totally submucous clefts among the PRS patients. There was no statistical difference between the groups in the prevalence of clefts in the relatives of the patients. The incidence of (genetically influenced) conical elevations in the lower lip was lowest in the noncleft subjects, high in ICP and highest in PRS children. The incidence of hypodontia, which acceptedly is genetically influenced, was also highest in the PRS group. Thus the foetal malposition with the tongue between the palatal shelves does not seem to play any decisive role in the pathogenesis of most PRS clefts. The cause for the PRS is more likely a genetically influenced growth disturbance in the maxilla and the mandible, which due to the organogenetic differences leads to diverging end results, micrognathia and cleft.