New blindness gene could help doctors save 1000s of people's sight

Main Category: Eye Health / Blindness
Article Date: 08 Nov 2004 - 10:00 PDT

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Scientists at Leeds University, UK, have located the faulty DNA code that is present in people with an unusual form of retinal disease that causes blindness, familial exudative vitreoretinopathy (FEVR) - this disease, and the DNA code fault runs in families. By locating this faulty gene, doctors may be able one day to save thousands of people's sight.

You can read about this study in the journal American Journal of Human Genetics.

The researchers examined people who had inherited FEVR. Many people with FEVR become blind because the vessels in the eye do not grow normally. Whether you lose your eyesight depends on how severe your FEVR is.

The researchers already knew of one gene on chromosome 11 that seemed to cause FEVR. However, it did not explain why everyone had FEVR. Dr. C Toomes and team discovered a second gene that was associated with FEVR - this second gene is also on chromosome 11.

The researchers reckon their findings could lead the way to new treatments for diabetic retinopathy and age related macular degeneration. They say their findings will also allow doctors to detect FEVR earlier and save people's sight as a result.

Dr C Toomes said "If we can understand the molecules that cause blood vessel development by looking at FEVR that might help us piece together the pathway for normal blood vessel growth and abnormal blood vessel growth."

About FEVR

Incomplete normal retinal angiogenesis is the hallmark of a group of retinal vascular diseases including familial exudative vitreoretinopathy (FEVR). The primary pathological process in FEVR is believed to be a premature arrest of retinal angiogenesis/vasculogenesis or retinal vascular differentiation, leading to incomplete vascularization of the peripheral retina (van Nouhuys 1991).

This failure to vascularize the peripheral retina is the unifying feature seen in all affected individuals, but by itself usually causes no clinical symptoms. The visual problems in FEVR result from secondary complications due to the development of hyperpermeable blood vessels, neovascularization and vitreo-retinal traction.

These features cause a reduction in visual acuity and in 20% of cases can lead to vitreous hemorrhage and partial or total retinal detachment. We have been using FEVR as a genetic model to understand this group of diseases. FEVR is a well-defined inherited disorder of retinal vessel development (MIM 133780) (Benson 1995, van Nouhuys 1991).

It is reported to have a penetrance of 100% but clinical features can be highly variable, even within the same family. Severely affected patients may be blind during the first decade of life, while mildly affected individuals may not even be aware of symptoms and are only diagnosed by fluorescein angiography (Ober et al. 1980). FEVR is genetically heterogeneous, and can be presented as autosomal dominant, autosomal recessive or X-linked traits.

Three loci have been mapped and two genes (Frizzled-4 gene, FZD4 , Robitaille et al 2002; LRP5, Toomes et al 2004b) have been identified in dominant FEVR.We are currently working to develop a disease classification and staging system.

Detailed information about FEVR is available on the OMIM, Online Mendelian Inheritance in Man website and at http://fevr.net, a site designed to orient patients with the signs and symptoms of FEVR and provide support for patients and families through education, outreach and understanding.

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