Correlation between speech outcome and cephalometric dimensions in patients with diastrophic dysplasia.

Diastrophic dysplasia (DTD) is a recessively inherited form of osteochondrodysplasia, presenting with disproportionate short stature and multiple orthopedic problems. The clinical oral manifestations include either cleft palate or submucous cleft palate in at least half of the patients. Histological studies have shown alterations in growth plate, articular, laryngeal, tracheal, and ear cartilages. Mutations in the DTDST gene, which codes for the sulphate transporter membrane protein, are responsible for the disease. Thirty-three patients were studied for speech characteristics and their correlation with cephalometric dimensions. Hyponasality was observed in 13 and misarticulation of /R/, /S/, or /L/ sounds in 17 of the 33 patients. Neither of these correlated with the occurrence of palatal deformities. Hyponasality was atypical and did not correlate with the obtained nasalance scores. Cephalometric measurements reflecting the size of the orofacial area of the vocal tract were short in the DTD patients compared with those in the healthy controls. The specific speech characteristics in DTD probably result from both the altered size and shape of the vocal tract and the structural and functional abnormalities of the laryngeal and tracheal cartilages.