Considering the presence of SLC26A4 mutations and thyroid function, we could identify three sub-groups of patients: group 1, non syndromic EVA (ns EVA, no SLC26A4 mutation and no thyroid dysfunction); group 2, EVA with DFNB4 (single SLC26A4 gene mutation and no thyroid dysfunction); group 3, EVA with Pendred Syndrome (two pathological mutation of SLC26A4 and thyromegaly with thyroid dysfunction).
Whole exome sequencing and/or Sanger sequencing of SLC26A4 in 117 individuals with sensorineural hearing loss with or without inner ear anomalies but not with goiter from Turkey, Iran, and Mexico were performed.
Pendred syndrome is an autosomal recessive disorder characterized by hearing loss and goiter and is caused by bi-allelic mutations (homozygous or compound heterozygous) of the PDS (SLC26A4) gene.
Clinical characteristics of patients with SLC26A4 mutations were congenital, fluctuating and progressive hearing loss usually associated with vertigo and/or goiter.
We propose using a combination of three parameters to define and diagnose PS: (i) sensorineural deafness with bilateral EVA; (ii) thyroid abnormality comprising goiter and/or hypothyroidism and/or a positive PDT; (iii) biallelic SLC26A4 mutations.
Loss of function mutations in pendrin protein cause Pendred syndrome, a disorder characterized by sensorineural deafness and a partial iodide organification defect that may lead to thyroid goiter.
The first one is named Pendred Syndrome (PS) when deafness is associated with thyroid goiter; the second is called DFNB4, when no other symptoms are present.
Results of this study stress the necessity of considering the analysis of SLC26A4 in molecular diagnosis of deafness especially when phenotypes such as goiter or enlarged vestibular aqueduct are present.
Recessive mutations of the SLC26A4 (PDS) gene on chromosome 7q31 can cause sensorineural hearing loss with goiter (Pendred syndrome) or non-syndromic autosomal recessive hearing loss (DFNB4).
Thyroid gland enlargement (goiter) appears to be primarily dependent on the presence of two mutant alleles of SLC26A4 in pediatric patients, but not in older patients.
Pendred syndrome, a combination of sensorineural deafness, impaired organification of iodide in the thyroid and goitre, results from biallelic defects in pendrin (encoded by SLC26A4), which transports chloride and iodide in the inner ear and thyroid respectively.
Mutations in SLC26A4 cause Pendred syndrome (hearing loss with goiter) or DFNB4 (non-syndromic hearing loss with inner ear malformation, such as enlarged vestibular aqueduct or Mondini deformity).
Deleterious mutations of SLC26A4 cause Pendred syndrome (PS), an autosomal recessive disorder comprising goitre and deafness with enlarged vestibular aqueducts (EVA), and nonsyndromic hearing loss (NSHL).
Mutations in SLC26A4 cause Pendred syndrome (PS) - hearing loss with goitre - or DFNB4 - non-syndromic hearing loss (NSHL) with inner ear abnormalities such as Enlarged Vestibular Aqueduct (EVA) or Mondini Dysplasia (MD).
It has been shown that mutations in the SLC26A4 gene are involved in syndromic deafness characterized by congenital sensorineural hearing impairment and goitre (Pendred's syndrome), as well as in congenital isolated deafness (DFNB4), both of which are associated with enlarged vestibular aqueduct (EVA).
The present study confirmed the clinical characteristics of patients with SLC26A4 mutations: congenital, fluctuating, and progressive hearing loss usually associated with vertigo and/or goiter during long-term follow-up.
It has been shown that mutations of the SLC26A4 (PDS) gene were involved in syndromic deafness characterized by congenital sensorineural hearing impairment and goitre (Pendred's syndrome), as well as in congenital isolated deafness (DFNB4).
Chloride uptake studies were made using HEK293-Phoenix cells expressing human wild type SLC26A4 (pendrin) and a mutant (SLC26A4(S28R)) we recently described in a patient with hypothyroidism, goiter and sensorineural hearing loss.
Our study illustrates that if only a single heterozygous SLC26A4/PDS mutation is found in a patient with goiter and deafness, other genetic explanations should be considered.
All patients harbouring mutations in the SLC26A4 gene had goiter and a positive perchlorate discharge test: 3 were slightly hypothyroid and 2 euthyroid.