Pattern dystrophy is an inherited retinal disease, meaning it is caused by changes, or mutations, in specific genes passed down from parents to their children. Understanding the genetic basis of pattern dystrophy is crucial for patients and their families, as it provides insights into how the disease is inherited, the risk to future generations, and the potential for future targeted therapies.
The vast majority of pattern dystrophy cases are linked to mutations in the PRPH2 gene (also known as the RDS gene). This gene is responsible for producing peripherin-2, a protein that is vital for the structural integrity of the light-sensing photoreceptor cells in the retina. When the PRPH2 gene is mutated, the photoreceptor cells cannot function correctly, leading to the accumulation of pigment in the macula and the characteristic visual symptoms of the disease.
Pattern dystrophy is almost always inherited in an autosomal dominant pattern. "Autosomal" means the mutated gene is located on one of the non-sex chromosomes, so it affects males and females equally. "Dominant" means that only one copy of the mutated gene (inherited from either the mother or the father) is sufficient to cause the disorder.
Because of this inheritance pattern, an individual with pattern dystrophy has a 50% chance of passing the mutated gene to each of their children. It is common to see a clear history of the condition across multiple generations in a family. However, pattern dystrophy is known for its "variable expressivity." This means that even within the same family, individuals carrying the exact same genetic mutation can experience very different symptoms. One family member might have severe vision changes in their 40s, while another might have only mild pigment changes and excellent vision well into their 70s. Furthermore, the specific "pattern" of pigment (e.g., butterfly-shaped vs. adult-onset vitelliform) can vary among affected relatives.
Given the genetic nature of the disease, genetic testing is highly recommended for individuals diagnosed with pattern dystrophy. A genetic test involves a simple blood or saliva sample and can confirm the specific gene mutation causing the condition. This confirmation is important for several reasons. It solidifies the diagnosis, helps differentiate pattern dystrophy from other macular conditions like age-related macular degeneration (AMD), and is often a prerequisite for participating in clinical trials for emerging gene therapies.
Genetic counseling is an essential companion to genetic testing. A genetic counselor can help patients and their families understand the test results, discuss the implications for family planning, and navigate the emotional aspects of an inherited condition. Patients should consult their healthcare provider to discuss whether genetic testing is appropriate for them and to get a referral to a qualified genetic counselor.