Usher syndrome is an inherited condition that causes both hearing loss and progressive vision loss due to retinitis pigmentosa (RP). It is the most common cause of combined deafness and blindness.

Pathophysiology
Usher syndrome results from mutations in genes involved in the development and function of specialized cells in the retina and inner ear. These mutations lead to abnormal development or degeneration of hair cells in the inner ear, causing hearing loss and progressive degeneration of photoreceptor cells in the retina, causing vision loss.

Genetic Transmission
Usher syndrome is inherited in an autosomal recessive pattern. This means:

• Both parents must carry a copy of the mutated gene to pass it on
• Each child of carrier parents has a 25% chance of inheriting the condition
• At least 11 genes have been associated with different types of Usher syndrome

Types:
There are three main clinical types:

• Type 1: Profound hearing loss or deafness at birth
  • Severe balance problems from birth – children often have delayed motor development and don’t walk until 18 months or later
  • Vision problems usually begin around age 10 or in early teens
  • Night blindness and loss of peripheral vision due to retinitis pigmentosa (RP)
• Type 2: Moderate to severe hearing loss at birth
  • Normal balance
  • Vision problems begin in late teens or early 20s
  • Night blindness and gradual loss of peripheral vision due to RP, but progression is typically slower than in Type 1
  • Central vision often retained into adulthood
• Type 3: Born with normal hearing and near-normal balance
  • Progressive hearing loss starting in childhood or teens
  • Vision loss begins in teens or early adulthood
  • Balance may deteriorate over time
  • About 50% experience balance problems

Signs and Symptoms

• Hearing loss (congenital or progressive)
• Progressive vision loss due to RP (night blindness, peripheral vision loss)
• Balance problems (mainly in Type 1)
• Delays in motor development in children (Type 1)

Potential Treatment Options
While there is no cure, management focuses on:

• Hearing aids or cochlear implants for hearing loss
• Low vision aids and mobility training for vision loss
• Vestibular rehabilitation for balance issues
• Genetic counseling for families for future conception
• Emerging therapies like gene therapy are under investigation

References

1. Arias-Peso, B., Calero-Ramos, M. L., López-Ladrón García de la Borbolla, C., López-Domínguez, M., Morillo-Sánchez, M. J., Méndez-Martínez, S., Sánchez-Gómez, S., & Rodríguez-de-la-Rúa, E. (2024). Multidisciplinary approach to inherited causes of dual sensory impairment. Graefe’s Archive of Clinical & Experimental Ophthalmology, 262(3), 701–715. https://doi.org/10.1007/s00417-023-06153-7
2. Castiglione, A., & Möller, C. (2022). Usher Syndrome. Audiology Research, 12(1), 42–65. https://doi.org/10.3390/audiolres12010005
3. Mahmood, R., Mahmood, F., Faisal, M. N., Mahmood, A., Muzaffar, H., Mahmood, M., Abbas, G., Mahmood, T., & Arshad, M. (2022). Usher Syndrome and Its Genetic Characterization. Pakistan Journal of Science, 74(5), 392–402
4. Miyoshi, T., Belyantseva, I. A., Sajeevadathan, M., & Friedman, T. B. (2024). Pathophysiology of human hearing loss associated with variants in myosins. Frontiers in Physiology, 01-18. https://doi.org/10.3389/fphys.2024.1374901

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