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Familial exudative vitreoretinopathy (FEVR, pronounced as fever) is a
Diagnosis of FEVR is often made through direct visualization of the retina and fluorescein angiography, along with personal and family medical history. Hallmark characteristics of FEVR include lack of blood vessels in the peripheral retina. Other findings may include vessel and macular dragging, sub-retinal exudates, neovascularization, retinal folds, and retinal detachments. FEVR must be differentiated from other diseases involving incomplete vascularization of the retina including retinopathy of prematurity (ROP), 
GeneReviews/NCBI/NIH/UW entry on Familial Exudative Vitreoretinopathy, Autosomal Dominant
NCBI Genetic Testing Registry
{{Other cell membrane protein disorders Blindness Disorders of choroid and retina
Familial exudative vitreoretinopathy (FEVR, pronounced as fever) is a genetic disorder
A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...
affecting the growth and development of blood vessels
The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...
in the retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which the ...
of the eye. This disease can lead to visual impairment and sometimes complete blindness in one or both eyes. FEVR is characterized by incomplete vascularization
Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature by processes of sprouting and splittin ...
of the peripheral retina. This can lead to the growth of new blood vessels which are prone to leakage and hemorrhage
Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, v ...
and can cause retinal folds, tears, and detachments. Treatment involves laser photocoagulation of the avascular portions of the retina to reduce new blood vessel growth and risk of complications including leakage of retinal blood vessels and retinal detachment
Retinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blin ...
s.
Information
Pathophysiology FEVR is caused by genetic defects involving the regulation of blood vessel growth in developing eyes. As a result, there is poor blood vessel growth to the periphery of the retina. The lack of blood supply to the peripheral retina triggers the release of molecules that stimulate blood vessel growth, such as vascular endothelial growth factor (VEGF). However, this new blood vessel growth, also known asneovascularization
Neovascularization is the natural formation of new blood vessels ('' neo-'' + '' vascular'' + '' -ization''), usually in the form of functional microvascular networks, capable of perfusion by red blood cells, that form to serve as collateral circu ...
, can lead to further complications such as the leakage and hemorrhage of retinal blood vessels, retinal tears, and detachments.
Genetics
There have been several gene mutations associated with FEVR. These genes code for proteins involved in the WNT signaling pathway
The Wnt signaling pathways are a group of signal transduction pathways which begin with proteins that pass signals into a cell through cell surface receptors. The name Wnt is a portmanteau created from the names Wingless and Int-1. Wnt signaling ...
, which is involved in the development of the human eye and regulation of blood vessel growth. Depending on the genes involved, FEVR can follow an autosomal dominant
In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...
, autosomal recessive
In genetics, dominance is the phenomenon of one variant ( allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant an ...
, or X-linked
Sex linked describes the sex-specific patterns of inheritance and presentation when a gene mutation (allele) is present on a sex chromosome (allosome) rather than a non-sex chromosome (autosome). In humans, these are termed X-linked recessive, ...
inheritance pattern. There is varying penetrance
Penetrance in genetics is the proportion of individuals carrying a particular variant (or allele) of a gene (the genotype) that also express an associated trait (the phenotype). In medical genetics, the penetrance of a disease-causing mutation is t ...
and expressivity depending on the genes involved. While genetic testing may be useful in the diagnosis of FEVR, a negative genetic test does not rule out the disease.
Diagnosis
Diagnosis of FEVR is often made through direct visualization of the retina and fluorescein angiography, along with personal and family medical history. Hallmark characteristics of FEVR include lack of blood vessels in the peripheral retina. Other findings may include vessel and macular dragging, sub-retinal exudates, neovascularization, retinal folds, and retinal detachments. FEVR must be differentiated from other diseases involving incomplete vascularization of the retina including retinopathy of prematurity (ROP), Norrie disease
Norrie disease is a rare disease and genetic disorder that primarily affects the eyes and almost always leads to blindness. It is caused by mutations in the ''Norrin cystine knot growth factor (NDP)'' gene, which is located on the X chromosome. ...
, Coat's disease, and others. Severity of disease is highly variable and can range from mild visual impairment to complete vision loss. Based on the severity of the disease, FEVR is diagnosed based on a clinical staging scale from 1 to 5. Since FEVR often runs in families, immediate relatives of someone diagnosed with FEVR should be examined by an ophthalmologist because the disease can have no symptoms before complications arise including retinal detachments.
Treatment
Treatment is largely aimed at reducing the amount of new blood vessel growth and preventing complications that may arise as a result, including retinal tears and detachments. Using a laser, an ophthalmologist burns the portions of the retina that are not supported by blood vessels, a technique known as laser photocoagulation. By doing so, this tissue will no longer release molecules that stimulate blood vessel growth. If a retinal detachment occurs, laser therapy or surgery
Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning "hand work". is a medical specialty that uses operative manual and instrumental techniques on a person to investigate or treat a pa ...
may be required to repair the retina.
References
External links
GeneReviews/NCBI/NIH/UW entry on Familial Exudative Vitreoretinopathy, Autosomal Dominant
NCBI Genetic Testing Registry
{{Other cell membrane protein disorders Blindness Disorders of choroid and retina