Pendred syndrome is an autosomal recessive disorder characterized by the 
association between sensorineural hearing loss and thyroid swelling or goitre 
and is likely to be the most common form of syndromic deafness. Within the 
thyroid gland of affected individuals, iodide is incompletely organified with 
variable effects upon thyroid hormone biosynthesis, whilst the molecular basis 
of the hearing loss is unknown. The PDS gene has been identified by positional 
cloning of chromosome 7q31, within the Pendred syndrome critical linkage 
interval and encodes for a putative ion transporter called pendrin. We have 
investigated a cohort of 56 kindreds, all with features suggestive of a 
diagnosis of Pendred syndrome. Molecular analysis of the PDS gene identified 47 
of the 60 (78%) mutant alleles in 31 families (includes three homozygous 
consanguineous kindreds and one extended family segregating three mutant 
alleles). Moreover, four recurrent mutations accounted for 35 (74%) of PDS 
disease chromosomes detected and haplotype analysis would favour common founders 
rather than mutational hotspots within the PDS gene. Whilst these findings 
demonstrate molecular heterogeneity for PDS mutations associated with Pendred 
syndrome, this study would support the use of molecular analysis of the PDS gene 
in the assessment of families with congenital hearing loss.