Abstract
Pendred syndrome (PS, OMIM #274600) is an autosomal recessive genetic disease, which becomes manifest in a combination of sensoric-neural deafness and dyshormonogenetic goitre. In the PS we frequently encounter abnormal formation of inner ear structures - enlarged vestibular aqueduct (EVA) and/or Mondini dysplasia (MD).
PS is caused by mutations in the SLC26A4 gene (called also PDS gene, OMIM *605646), which encodes the anion transporter pendrin, expressed especially in thyroid gland and the inner ear. Pendrin in the thyroid gland is localized on the apical pole of thyreocytes.
Its main function is the transport of iodine into colloids in follicle lumen, where it is subsequently bound to organic molecules. The affection of thyroid gland in the Pendred syndrome becomes manifest mostly in the second decade of life under the picture of euthyroid and hypothyroid goitre, rarely there is dyshormogenesis at birth and the disease is then diagnosed in the newborn screening for congenital hypothyreosis.
The mutation in the SLC26A4 gene causes also a non-syndrome hearing loss associated with EVA (formerly called DFNB4, OMIM #600791). Only recently the digenetic heredity has been established - mutation in the SLC26A4 gene in combination with a mutation in the FOXI1 gene (OMIM *601093) or KCNJ10 gene (OMIM *602208).
PS represents the most frequent syndrome deafness and the SLC26A4 gene is apparently the second most frequent gene responsible for AR non-syndrome hearing loss (after GJB2 gene for Connexin 26, which is responsible for 40% of AR non-syndrome hearing loss).A recently undertake study in the Czech Republic confirmed mutation in the SLC26A4 gene in 8.5% of predominantly child patients with inborn hearing loss; however only less than 27% of these children displayed a completely expressed PS (after puberty in all of them). Thanks to molecular genetic examination it is the-refore possible to predict with high probability the development of thyroid gland disorder and to prevent the development of goitre by an early intervention.
The examination of the SLC26A4 gene in presently available in the Czech Republic.