Pendred's syndrome is an autosomal recessive disease characterized by goiter and 
congenital sensorineural deafness. Most patients with Pendred's syndrome are 
euthyroid, but the perchlorate test is positive indicating an impaired iodide 
organification. The sensorineural deafness is typically associated with a 
malformation of the inner ear, referred to as Mondini cochlea. The incidence of 
Pendred's syndrome is thought to be as high as 7.5 to 10 in 100,000 individuals, 
and it has been estimated to account for about 10% of the cases with hereditary 
deafness. Linkage of Pendred's syndrome to chromosome 7q22-31.1 was first 
established in 1996, and the Pendred's syndrome gene (PDS gene) was cloned in 
1997. The PDS gene encodes pendrin, a highly hydrophobic 780 aminoacid protein 
with 11 transmembrane domains. Its function is unknown. Sequence comparison 
reveals a very high homology to several sulfate transporters suggesting that it 
could be a sulfate or anion transporter. A wide spectrum of mutations in the PDS 
gene has now been associated with Pendred's syndrome. Molecular analysis of the 
PDS gene is useful to make a definite diagnosis in familial and sporadic cases 
with Pendred's syndrome, and will be helpful for determining the true prevalence 
of this disorder.