How do Inherited Retinal Diseases Happen?

The abbreviation IRD refers to a group of hereditary conditions called retinal diseases. Genes contain DNA, also known as “deoxyribonucleic acid.” A gene contains the instructions necessary for the development and operation of the retinal cells in our bodies. A “mistake” or alteration in one or more genes causes IRDs. Because of this, retinal cells don’t function properly, which eventually results in vision loss. Already, 250 genes have been linked to IRD.

There are many more genes, but they haven’t all been discovered. Each IRD may be passed down differently within a family from one generation to the next. It’s possible that you or a member of your family has an IRD. You might be the oldest member of your family.

The most prevalent retinal dystrophy, affecting 1 in 3000 people, is retinal pigmentosa. The first mutation linked to a human disease was found through family studies of its X-linked form. It is now known that retinitis pigmentosa is remarkably genetically heterogeneous, with over 150 mapped chromosomal loci and 100 genes in charge of the phenotype. Thus, the retinitis pigmentosa phenotype is now seen as a final common clinical pathway.

It develops from a number of reasons that cause rod photoreceptor degeneration rather than as a single phenotypic entity.

Unified by the presence of night-blindness, progressive visual field loss, eventual acuity loss, and bone-spicule retinal pigmentation.

Cones appear to degenerate secondarily to rods rather than being directly affected by the mutations that cause retinitis pigmentosa.

The majority of retinitis pigmentosa mutations only affect rods. The genes involved serve a wide range of functions, including encoding structural and transmembrane proteins, transcription factors, and proteins for phototransduction. Each results in the death of rod photoreceptor cells by apoptosis, a form of programmed cell death, through pathways that are currently unknown. Cones appear to degenerate secondarily to rods rather than being directly affected by the mutations that cause retinitis pigmentosa.

It explains why complete blindness and loss of central vision are occasionally observed at the end stage of the disease. The most severe retinal dystrophies are those caused by Leber congenital amaurosis. Individuals who are affected typically show profound blindness, roving nystagmus, variable retinal pathology, and occasionally other systemic pathology in the first year of life. Leber congenital amaurosis is now known to be caused by at least six genes, in contrast to earlier theories based on an ostensibly distinctive and unifying phenotype.