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Why take a genetic test?
Some IRDs are caused by the one mutation in a specific gene. For example, Choroideremia is caused by a mutation to the CHM gene. However, it is not always so straightforward. Retinitis Pigmentosa can be caused by over 80 different genes – so unless you have had a genetic test, it is very unlikely you will know which mutation is causing your IRD!
Knowing the exact IRD and the underlying causative mutation will provide patients with knowledge about:
- The inheritance pattern of the condition
- Prognosis, or medical progression of the condition
- The possibility of joining a patient registry
- Participating in an appropriate clinical trial
- Risk to other organ systems, in the case of syndromic diseases
- Accessing treatments should they be available (in the future)
Nearly 300 IRD-associated genes have now been discovered, yet this only yet this only permits for definitive genetic diagnoses for 2 of every 3 IRD patients. Routine affordable and accessible genetic testing will fast-track the discovery of the remaining genes, and pave the way for therapeutic intervention for everyone affected by IRDs.
Further considerations regarding genetic testing
Below are some of the benefits and limitations to pursuing genetic testing:
Benefits:
- A genetic test has the potential to identify the exact cause of an IRD.
- It allows people to adjust their lifestyle and manage their particular condition as well as possible.
- Receiving an accurate diagnosis makes it possible for an individual to participate in appropriate clinical trials and allows for access to relevant treatments, should they become available. These opportunities are only available to those who have undergone a genetic test.
- The results of a genetic test can also be stored on a register that will help to not only populate clinical trials in the future, but help researchers to better understand the molecular basis of the condition.
- For some, the results of a genetic test can assist in family planning decisions. Being aware that there is an increased risk of having a child with an IRD can also allow you to talk with your doctor to best plan for your future and prepare yourself, should you choose to have a family.
- As most genetic conditions are inherited and affects many generations of a family, information about your genetic makeup (genotype) can be useful to other family members. For example, in some cases the risk of having a baby with a retinal dystrophy is not for the affected person but for a relative, which is evident in IRDs that have an X-linked pattern of inheritance.
Limitations
Emotional burden
It must be emphasised that taking a genetic test, waiting for, and ultimately receiving the results can be a very stressful and emotional experience for an individual and their family. Those who are eventually diagnosed with IRDs often describe the actual diagnosis as a relief, because they now have a definitive answer and feel empowered to make informed life decisions. However, some have also described feelings of anxiety and guilt, particularly when disease-causing mutations have been passed on to their children. With this in mind, it is crucial to talk through the possible outcomes, be they positive or negative, of a genetic test with your loved ones. Support is also available to you through your genetic counsellor.
Limited therapeutic options
As many treatments for IRDs are still in the development phase, a genetically confirmed diagnosis may not lead to an intervention or treatment now or in the future. Although nearly 300 IRD-associated genes have been identified, they provide definitive diagnoses to only 2 of every 3 individuals living with an IRD. It is very important to note that in some cases, the gene(s) responsible for a genetic condition have not been identified. Some genetic mutations are very difficult to find with current laboratory techniques. For those trying to get a diagnosis to enable access to information on inheritance and disease pathways, this can be very frustrating.
Fear of discrimination
While many countries now have legislation protecting individuals from discrimination on account of a genetic diagnosis – particularly with matters such as employment or health insurance, many may be wary of the impact a genetic test may have. These are valid concerns, and we encourage you to discuss any questions you may have with your physician, genetic counsellor, or local advocacy organisation. See our FAQs on Health Insurance & Genetic Discrimination for more information.