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Pendred syndrome

pendred syndrome, pendred syndrome and dfnb4 hearing loss
Pendred syndrome or Pendred disease is a genetic disorder leading to congenital bilateral both sides sensorineural hearing loss and goitre with euthyroid or mild hypothyroidism decreased thyroid gland function There is no specific treatment, other than supportive measures for the hearing loss and thyroid hormone supplementation in case of hypothyroidism It is named after Dr Vaughan Pendred 1869–1946, the English doctor who first described the condition in an Irish family living in Durham in 189612 It accounts for 75% of all cases of congenital deafness3

Contents

  • 1 Signs and symptoms
  • 2 Genetics
  • 3 Pathophysiology
  • 4 Diagnosis
  • 5 Treatment
  • 6 References
  • 7 External links

Signs and symptomsedit

The hearing loss of Pendred's syndrome is often, although not always, present from birth, and language acquisition may be a significant problem if deafness is severe in childhood The hearing loss typically worsens over the years, and progression can be step-wise and related to minor head trauma In some cases, language development worsens after head injury, demonstrating that the inner ear is sensitive to trauma in Pendred syndrome; this is as a consequence of the widened vestibular aqueducts usual in this syndrome3 Vestibular function varies in Pendred syndrome and vertigo can be a feature of minor head trauma A goitre is present in 75% of all cases3

Geneticsedit

Pendred syndrome has an autosomal recessive pattern of inheritance

Pendred syndrome inherits in an autosomal recessive manner, meaning that one would need to inherit an abnormal gene from each parent to develop the condition This also means that a sibling of a patient with Pendred's syndrome has a 25% chance of also having the condition if the parents are unaffected carriers

It has been linked to mutations in the PDS gene, which codes for the pendrin protein solute carrier family 26, member 4, SLC26A4 The gene is located on the long arm of chromosome 7 7q3145 Mutations in the same gene also cause enlarged vestibular aqueduct syndrome EVA or EVAS, another congenital cause of deafness; specific mutations are more likely to cause EVAS, while others are more linked with Pendred syndrome6

Pathophysiologyedit

SLC26A4 can be found in the cochlea part of the inner ear, thyroid and the kidney In the kidney, it participates in the secretion of bicarbonate However, Pendred's syndrome is not known to lead to kidney problems7 It functions as an iodide/chloride transportercitation needed In the thyroid, this leads to reduced organification of iodine ie its incorporation into thyroid hormone4

Diagnosisedit

Audiometry measuring ability to hear sounds of a particular pitch is usually abnormal, but the findings are not particularly specific and an audiogram is not sufficient to diagnose Pendred's syndrome A thyroid goitre may be present in the first decade and is usual towards the end of the second decade MRI scanning of the inner ear usually shows widened or large vestibular aqueducts with enlarged endolymphatic sacs and may show abnormalities of the cochleae that is known as Mondini dysplasia3 Genetic testing to identify the pendrin gene usually establishes the diagnosis If the condition is suspected, a "perchlorate discharge test" is sometimes performed This test is highly sensitive, but may also be abnormal in other thyroid conditions3 If a goitre is present, thyroid function tests are performed to identify mild cases of thyroid dysfunction even if they are not yet causing symptoms8

Treatmentedit

No specific treatment exists for Pendred syndrome Speech and language support and cochlear implants may improve language skills8 If thyroid hormone levels are decreased, thyroid hormone supplements may be required Patients are advised to take precautions against head injury8

Referencesedit

  1. ^ Pendred V 1896 "Deaf-mutism and goitre" Lancet 2 3808: 532 doi:101016/S0140-67360174403-0 
  2. ^ Pearce JM 2007 "Pendred's syndrome" Eur Neurol 58 3: 189–90 PMID 17622729 doi:101159/000104724 
  3. ^ a b c d e Reardon W, Coffey R, Phelps PD, et al July 1997 "Pendred syndrome--100 years of underascertainment" PDF QJM 90 7: 443–7 PMID 9302427 doi:101093/qjmed/907443 
  4. ^ a b Sheffield VC, Kraiem Z, Beck JC, et al April 1996 "Pendred syndrome maps to chromosome 7q21-34 and is caused by an intrinsic defect in thyroid iodine organification" Nat Genet 12 4: 424–6 PMID 8630498 doi:101038/ng0496-424 
  5. ^ Coyle B, Coffey R, Armour JA, et al April 1996 "Pendred syndrome goitre and sensorineural hearing loss maps to chromosome 7 in the region containing the nonsyndromic deafness gene DFNB4" Nat Genet 12 4: 421–3 PMID 8630497 doi:101038/ng0496-421 
  6. ^ Azaiez H, Yang T, Prasad S, et al December 2007 "Genotype-phenotype correlations for SLC26A4-related deafness" Hum Genet 122 5: 451–7 PMID 17690912 doi:101007/s00439-007-0415-2 
  7. ^ Royaux IE, Wall SM, Karniski LP, et al March 2001 "Pendrin, encoded by the Pendred syndrome gene, resides in the apical region of renal intercalated cells and mediates bicarbonate secretion" Proc Natl Acad Sci USA 98 7: 4221–6 PMC 31206  PMID 11274445 doi:101073/pnas071516798 
  8. ^ a b c National Institute on Deafness and Other Communication Disorders October 2006 "Pendred Syndrome" Retrieved 2008-05-05 

External linksedit

  • GeneReviews/NCBI/NIH/UW entry on Pendred Syndrome/DFNB4
  • NCBI Genes and Diseases

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