Dominant inheritance of velopharyngeal incompetence.

A family is described in which a girl, two boys and their father showed speech hypernasality. A half-sib, a grandfather, a great-aunt, and a cousin of these sibs also showed a similar speech defect. Analysis of recorded speech of the father and three sibs revealed articulation deficiencies in addition to hypernasality. Intra-oral examination and neurologic evaluation of the cranial nerves failed to reveal any abnormality in palate morphology or cranial nerve function. Psychometric and audiometric studies of the affected did not contribute to an explanation of the defect. Speech cinefluoroscopy and cephalometric radiographs confirmed that the speech defect involved velopharyngeal incompetence resulting from an anatomic disproportion of the velopharyngeal structures. The family pedigree supports the concept that this type of nasal speech, resulting from disproportion of velopharyngeal structures, is transmitted as an autosomal dominant trait.