Pendred syndrome : Phenotypic heterogeneity in two families carrying the same PDS missense mutation. H. Ayadi¹, S. Masmoudi¹, I. Charfeddine², M. Hmani¹, M. Grati³, A. Ghorbel², A. Boulila-Elgaed¹, J.P. Hardelin³, M. Drira². 1) Dept Immunology, Fac de Medecine de Sfax, Sfax, Tunisia; 2) Service d'ORL, CHU H. Bourguiba, 3018 Sfax, Tunisie; 3) Unit de gntique des dficits sensoriels, Institut Pasteur, 25, rue du Dr. Roux, 75725 Paris 15, France.

   
Pendred syndrome is a recessively inherited disease which is classically defined as the association of congenital sensorineural hearing loss, thyroid goitre and positive perchlorate discharge test. This disease has recently been shown to be caused by mutations in the PDS gene, which encodes an anion transporter called pendrin. Molecular analysis of the PDS gene was performed in two consanguineous large families from Southern Tunisia comprising a total of 23 individuals affected with profound congenital deafness; the same missense mutation, L445W, was identified in all affected individuals. Widened vestibular aqueducts were found in all the patients who underwent CT scan exploration of the inner ear. In contrast, goitre was present only in 11 affected individuals, who interestingly had a normal perchlorate discharge test whenever performed. Therefore, the present results further question the sensitivity of the perchlorate test for the diagnosis of Pendred syndrome and would support the use of a molecular analysis of the PDS gene in the assessment of individuals with severe to profound congenital hearing loss associated with inner ear morphological anomaly, even in the absence of a thyroid goitre.