Pendred syndrome is an autosomal recessive disorder characterised by 
sensorineural hearing loss and thyroid dyshormonogenesis. It is caused by 
mutations in the PDS/SLC26A4 gene (OMIM 605646) encoding for pendrin. 
Hypothyroidism in Pendred syndrome can be--although rarely--present from birth 
and therefore diagnosed by neonatal screening. The aim of our study was to 
identify patients with Pendred syndrome among a historical cohort of patients 
with congenital hypothyroidism (CH) identified by neonatal screening, and to 
find their mutations in the PDS/SLC26A4 gene. We investigated 197 Czech 
Caucasian children with CH detected by the neonatal screening between the years 
1985 and 2005. The clinical diagnosis of Pendred syndrome was based on the 
laboratory and sonographic signs of thyroid dyshormonogenesis in association 
with sensorineural hearing loss. In subjects clinically diagnosed with Pendred 
syndrome, we sequenced all exons and exon-intron boundaries of the PDS/SLC26A4 
gene. Hearing loss was present in 10/197 children with screening-detected CH. Of 
these, three fulfilled the diagnostic criteria of Pendred syndrome. Two patients 
were compound heterozygotes for PDS/SLC26A4 mutations: patient 1 carried 
c.2089+1G>A / c.3G>C and patient 2 carried p.Tyr530His / p.Val422Asp. Two of the 
four identified mutations were novel (c.3G>C in patient 1 and p.Val422Asp in 
patient 2). The third patient was free of mutations in the PDS/SLC26A4 gene, 
representing a phenocopy. In conclusion, our results indicate the rarity of 
Pendred syndrome as a cause of CH. The identification of two novel mutations 
expands the spectrum of mutations in the PDS/SLC26A4 gene and emphasizes their 
marked allelic heterogeneity.