Pendred syndrome: Clinical characteristics and molecular basis

Pendred syndrome (OMIM 274600) is an autosomal, recessive disorder defined by the triad of congenital deafness, goiter, and positive perchlorate test. After the cloning of the Pendred syndrome (PDS) gene in 1997, a century after the recognition of the curious association of goiter and deaf-mutism by Vaugham Pendred in 1896, the elucidation of the molecular basis of Pendred syndrome has resulted in fascinating and surprising observations. It has become apparent that mutations in this gene are not only associated with PDS, but they form the molecular basis of nonsyndromic autosomal recessive deafness DFNB4 (OMIM 600791) and nonsyndromic familial enlarged vestibular aqueduct (OMIM 603545). These nonsyndromic forms of hearing impairment are therefore allelic variants of the syndromic deafness characterizing Pendred syndrome. The recent functional characterization of pendrin, the protein encoded by the PDS gene, as a transporter of iodide and chloride is a key step in further elucidating its role in the pathophysiology of both the inner ear and thyroid follicular cells.