Pendred syndrome is an autosomal recessive disorder characterized by congenital 
sensorineural deafness, goiter, and impaired iodide organification. It is caused 
by mutations in the PDS gene. Most published mutation studies of Pendred 
syndrome have dealt with Western populations. In this study, we examined 
clinical and molecular characteristics of 16 affected individuals in 6 unrelated 
Thai families. Of all the affected, 100% (16/16) had bilateral deafness, 68.8% 
(11/16) goiters, and 25% (4/16) hypothyroidism. Follicular thyroid carcinoma and 
Hürthle cell adenoma were found in affected members of a family, raising the 
possibility of an increased risk of thyroid carcinoma in Pendred syndrome 
patients. Sequence analysis of the entire coding region of the PDS gene 
successfully identified all 12 mutant alleles in these 6 families. The 12 
identified mutant alleles constituted 6 distinct mutations including 3 splice 
site mutations (IVS4-1G>A, IVS7-2A>G, IVS9- 1G>A), one frame shift mutation 
(1548insC) and 2 missense mutations (T67S, H723R). Eight mutations out of 12 
were constituted by IVS7- 2A>G and 1548insC, each one being present in 4 
distinct alleles in our studied group. The identification of these two frequent 
PDS mutations will facilitate the molecular diagnosis of Pendred syndrome in 
Thai populations. In addition, three newly identified mutations, T67S, 
IVS4-1G>A, and IVS9-1G>A, were not observed in 50 unrelated healthy Thai 
controls.