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Diagram showing the different types of inherited retinal dystrophy, the gene mutations that cause them and the overlap between different IRDs

Adapted from Leroy et al., 2018.9

Inherited retinal dystrophy:
an overview

IRDs are a group of rare diseases associated with an inherited gene mutation affecting the retina that involve deterioration of vision and can result in eventual blindness.2‑6

Different forms of IRD differ in onset, severity, and progression of the diseases depending on the type of mutation and the cells affected.2,5,6

While there are differences between IRDs, they share some common features:

  • The diseases are inherited and are caused by a specific genetic mutation(s). Depending on the IRD, blindness or vision loss may occur at birth or later in life.6
  • Vision loss ultimately results from damage to the retina.6 IRDs are characterized by the progressive deterioration of rods and cones.3,8,9
  • Retinal damage is caused by specific genetic mutations that affect how retinal cells function and survive.6 
  • There are currently over 300 genes that have been identified as being associated with IRD.6,10 
  • Different forms of IRD have different inheritance patterns depending on the mutations responsible.6 For example, Usher syndrome is always caused by an autosomal recessive mutation, although not always in the same gene. Others, such as Leber congenital amaurosis, are usually autosomal recessive inheritance, but can also present in autosomal dominant forms.7 
  • Some IRDs, such as choroideremia or X-linked retinoschisis are caused by one or only a small number of genes. Other diseases can be caused by many different mutations in many different genes. For example, over 64 genes have been identified that cause retinitis pigmentosa.6 
  • Retinitis pigmentosa, which is more of a collection of degenerations, can be autosomal recessive, autosomal dominant, or X-linked depending on the specific mutation(s) and genes involved.7,8,11

Common forms of IRD

Common forms of IRD
common forms of ird

IRD and genetic testing

IRDs have overlapping signs and symptoms that can make it difficult to be sure about a confirmed diagnosis: a genetic test may help to unlock a diagnosis for your patient.3,9

DNA strand

There are over 300 genes currently associated with IRDs6,10

Stethoscope

To provide early and accurate diagnosis9,18

Yoga pose

A specific diagnosis may help reduce anxiety9

Magnifying glass

To guide the testing of family members, identifying those at risk of inheriting or passing on the condition18

References
1. World Health Organization. https://www.who.int/blindness/causes/priority/en/index9.html. Accessed July 2, 2020.
2. Chung DC, Bertelsen M, Lorenz B, et al. Am J Ophthalmol. 2019;199:58-70.
3. Duncan JL, Pierce EA, Laster AM, et al. Trans Vis Sci Technol. 2018;7(4):6.
4. Russell S, Bennett J, Wellman JA, et al. Lancet. 2017;390(10097):849-860.
5. Patel U, Boucher M, de Léséleuc L, Visintini S. In: CADTH issues in emerging health technologies. Canadian Agency for Drugs and Technologies in Health issue: 2018:169.
6. Fighting Blindness Canada. https://www.fightingblindness.ca/resources/genetic-testing-for-inherited-retinal-diseases/. Reviewed October 2020. Accessed January 18, 2021.
7. Tsang SH, Sharma T, eds. Atlas of inherited retinal diseases. Adv Exp Med Biol. Cham, Switzerland: Springer; 2018.
8. Dolz-Marco R, Boon C, Gallego-Pinazo, Chhablani J. In: Chhablani J, Ruiz-Medrano J, eds. Choroidal Disorders. Academic Press; 2017: 63-72.
9. EyeNet. https://www.aao.org/Assets/bebfbaef-a092-45b0-9883-c563331546ae/636649294795430000/july-2018-eyenet-supplement-pdf?inline=1. Accessed June 16, 2020.
10. Daiger SP. RetNet. https://sph.uth.edu/retnet/sum-dis.htm. Accessed July 2, 2020.
11. Foundation Fighting Blindness. https://www.fightingblindness.org/genetic-testing-for-retinal-degenerative-diseases-information-and-resources-for-affected-individuals-families-and-health-care-providers. Accessed January 18, 2021.
12. Fighting Blindness Canada. https://www.fightingblindness.ca/eye-diseases-pathways/retinitis-pigmentosa/. Reviewed August 2018. Accessed March 3, 2021.
13. Andrews C, Sunderland M. Fighting Blindness Canada Website. https://www.fightingblindness.ca/eye-diseases-pathways/usher-syndrome/. Updated on August 23, 2018. Accessed March 3, 2021.
14. Fighting Blindness Canada. https://www.fightingblindness.ca/eye-diseases-pathways/leber-congenital-amaurosis/. Accessed March 3, 2021.
15. Andrews C, Sunderland M. Fighting Blindness Canada Website. https://www.fightingblindness.ca/eye-diseases-pathways/stargardt-disease/. Updates August 23, 2018. Accessed March 3, 2021.
16. National Eye Institute. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/stargardt-disease. Updated July 10, 2019. Accessed March 4, 2021.
17. Fighting Blindness Canada. https://www.fightingblindness.ca/eye-diseases-pathways/bardet-biedl-syndrome/. Accessed March 3, 2021.
18. American Academy of Ophthalmology. https://www.aao.org/clinical-statement/recommendations-on-clinical-assessment-of-patients. Published 2016. Accessed July 2, 2020.
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