Hereditary deafness and phenotyping in humans.

Area of Science:

• Genetics
• Otolaryngology
• Molecular Biology

Background:

• Hereditary deafness is genetically diverse, with numerous genes linked to dominant and recessive forms.
• Despite advances, pinpointing the genetic cause of hearing loss in individuals remains challenging.
• Clinical evaluation and phenotypic clues are crucial for diagnosing hearing loss, especially to rule out syndromic causes.

Purpose of the Study:

• To propose a clinical approach for investigating the causes of hearing loss.
• To highlight key investigations and genetic screening strategies for identifying the etiology of deafness.
• To emphasize the importance of genotype-phenotype correlation in hereditary hearing loss.

Main Methods:

• Clinical assessment including ophthalmology review, renal ultrasound, and petrous temporal bone neuro-imaging.
• Molecular screening of the GJB2 (Connexin 26) gene for non-syndromic deafness.
• Consideration of mitochondrial inheritance in multigenerational families, especially with aminoglycoside exposure.
• Review of specific genetic loci (e.g., DFNB2, DFNA1) and their associated phenotypes.

Main Results:

• GJB2 (Connexin 26) screening is recommended for unidentified non-syndromic deafness due to its prevalence and straightforward testing.
• Mitochondrial inheritance should be considered in specific family histories.
• Various non-syndromic recessive and dominant deafness forms present with distinct audiometric patterns and radiological findings, or associated symptoms.

Conclusions:

• A systematic clinical approach combined with targeted molecular testing is essential for diagnosing hereditary hearing loss.
• Understanding the genetic heterogeneity and specific phenotypes aids in selecting appropriate diagnostic investigations.
• Continued clinical evaluation and genotype-phenotype correlation will refine molecular testing strategies for deafness.