“…It is considered the most common cause of congenital deafness, but the actual incidence of the syndrome is difficult to establish because of the variable phenotype of affected subjects, even within the same family (2)(3)(4). In the last 3 y PS has been associated, with a homozygous or compound heterozygous pattern, to mutations in the PDS gene (5)(6)(7)(8)(9)(10)(11)(12)(13)(14). PDS maps on chromosome band 7q22-31.1 and codes for pendrin (7), a transmembrane protein, which was first found to be expressed in the thyroid and in particular at the apical surface of the thyroid cell, where it likely functions as an iodide-chloride transporter (15)(16)(17).…”