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G508 Deafness in a family with complex phenotype-genotype presentations
  1. S Ratnayake,
  2. S Dhindsa
  1. Paediatrics, The Royal Wolverhampton NHS Trust, Wolverhampton, UK

Abstract

Aim Genetic causes are thought to be responsible for approximately 50%–60% of cases of hearing impairment. Our aim is to demonstrate the complexity of phenotype-genotype presentations in a family with sensorineural deafness.

Method This is a retrospective case study of a family including family history, audiometry, radiology and genetic investigations.

Results A 5 year old girl moved into the local area with progressive bilateral sensorineural deafness, initially identified through newborn hearing screening. She wears bilateral digital hearing aids with excellent aided hearing thresholds. Neuroimaging revealed evidence of bilateral widened vestibular aqueducts, with decreased cochlear partitioning. Genetic studies showed homozygous SLC26A4 mutations, confirming Pendred syndrome. Parents were non-consanguineous but both were carriers for the mutation and this confirmed the expected autosomal recessive inheritance. The child was clinically and biochemically euthyroid. Urinalysis and Ophthalmology were normal. Newborn blood spot for congenital CMV was negative. Additionally, she had a heterozygous mutation in the Connexin 26 gene (c.71G>A). The clinical significance of this is yet unknown. The maternal aunt was reported to be a sign language user due to congenital deafness from an unknown cause. Due to the genetic aetiology, family audiometry was undertaken. Both parents, in their early 40’s with no noise exposure, unexpectedly had bilateral mild sensorineural hearing loss, predominantly affecting the high-frequencies. This is not explained by the parental Pendred carrier status. Further complicating the family aetiology, mother had strong evidence of 3+ microscopic haematuria. Alport syndrome was suspected but the specific genes (COL4A3, COL4A4 and COL4A5) did not show mutations. Hence, the cause of her mother’s deafness and its relationship to the child is yet unknown. Her father has normal urinalysis. Her 10-year-old sister has normal audiometry and urinalysis.

Discussion A seemingly obvious cause of sensorineural deafness in a child may not always explain the aetiology in a family. It is therefore important to keep an open-mind and investigate family members, which will have implications for the future. In the UK, national initiatives such as the 1 00 000 Genomic Project may shed more light in the future on complex situations like this.

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