Long-term hearing threshold-on-age follow-up data, including non-linear 
regression analysis, are given for 12 consecutive Pendred patients. The clinical 
diagnosis of Pendred's syndrome was confirmed by a mutation analysis of the PDS 
gene in 11 out of the 11 cases tested. Recent imaging of the temporal bones in 
seven out of these 12 patients showed widened vestibular aqueducts in each case. 
The diagnostic perchlorate test was negative in one patient, but this test was 
positive in her affected sister. Mutation analysis of the PDS gene in these 
patients confirmed that Pendred's syndrome is a monogenetic disorder. 
Progressive sensorineural hearing loss and widened vestibular aqueducts are 
characteristic features of Pendred's syndrome, which provides the opportunity to 
diagnose Pendred's syndrome clinically in the first few years of life, as has 
recently been suggested in a case report (Cremers et al., Progressive 
sensorineural hearing loss and a widend vestibular aqueduct in Pendred syndrome, 
Arch. Otolaryngol. 124 (1998) 501-505). Mutation analysis of the involved gene 
can be used to confirm the clinical diagnosis.