Autosomal Dominant Vitreoretinochoroidopathy

Autosomal Dominant Vitreoretinochoroidopathy, or ADVIRC, is a very rare genetic eye condition that affects how the eye develops and functions. It is caused by a change (mutation) in a specific gene called BEST1, which is responsible for making a protein that helps keep the cells in the back of the eye healthy. In ADVIRC, this protein doesn't work correctly, leading to problems in several parts of the eye, including the clear gel inside the eye (the vitreous), the light-sensitive layer at the back (the retina), and the blood vessels underneath it (the choroid). People with ADVIRC often have eyes that are slightly smaller than normal, a condition called microcornea, and they may be far-sighted. A key sign that eye doctors look for is a distinct, dark ring of pigment in the outer edges of the retina. While central vision is usually normal in the early stages of life, the condition can cause a slow decline in vision over time. Patients are also at a higher risk for developing other eye problems at a younger age than usual, such as cataracts (clouding of the eye's lens) and glaucoma (increased pressure inside the eye), which can further affect their sight. Because ADVIRC can affect vision in multiple ways, it is important for patients to have regular, comprehensive eye exams. While there is currently no cure for the underlying genetic cause, many of the complications can be treated. For example, glasses can help with far-sightedness, and surgery or medications can be used to manage cataracts and glaucoma. Monitoring the retina is also crucial so that any swelling or abnormal blood vessel growth can be treated promptly to help preserve vision for as long as possible.

Condition category: Vitreoretinal Disorder

Prevalence: Less than 1 in 1,000,000

Inheritance patterns: Autosomal Dominant

Age of onset: First decade of life

Clinical overview: Autosomal dominant vitreoretinochoroidopathy (ADVIRC) is a rare, inherited pan-ophthalmic disorder belonging to the spectrum of bestrophinopathies. It is caused by specific heterozygous mutations in the BEST1 gene. Unlike other bestrophinopathies that primarily affect the macula, ADVIRC is characterized by a unique combination of progressive vitreoretinal degeneration and developmental anomalies of the eye. The condition typically presents in the first decade of life and exhibits significant phenotypic variability and variable expressivity, even among members of the same family. The hallmark clinical feature of ADVIRC is a distinct, 360-degree circumferential band of chorioretinal hyperpigmentation located in the peripheral retina, usually between the vortex veins and the ora serrata. This band has a sharply demarcated posterior boundary, separating the affected peripheral retina from the relatively normal-appearing central retina. Associated fundus findings include preretinal punctate white opacities, retinal arteriolar narrowing, and fibrillar condensation or liquefaction of the vitreous. In the early stages, the macula is typically spared, but as the disease progresses, patients may develop cystoid macular edema, epiretinal membranes, or chorioretinal macular atrophy. In addition to the posterior segment findings, ADVIRC is strongly associated with anterior segment developmental anomalies. These include microcornea, a shallow anterior chamber, nanophthalmos (abnormally small eyes), and hyperopia. These structural abnormalities predispose patients to a high risk of developing narrow-angle or acute angle-closure glaucoma. Early-onset presenile cataracts are also a common feature. The combination of these anterior and posterior segment manifestations makes ADVIRC a complex disorder requiring comprehensive ophthalmic management.

Patient and family guide: Autosomal Dominant Vitreoretinochoroidopathy, or ADVIRC, is a very rare genetic eye condition that affects how the eye develops and functions. It is caused by a change (mutation) in a specific gene called BEST1, which is responsible for making a protein that helps keep the cells in the back of the eye healthy. In ADVIRC, this protein doesn't work correctly, leading to problems in several parts of the eye, including the clear gel inside the eye (the vitreous), the light-sensitive layer at the back (the retina), and the blood vessels underneath it (the choroid). People with ADVIRC often have eyes that are slightly smaller than normal, a condition called microcornea, and they may be far-sighted. A key sign that eye doctors look for is a distinct, dark ring of pigment in the outer edges of the retina. While central vision is usually normal in the early stages of life, the condition can cause a slow decline in vision over time. Patients are also at a higher risk for developing other eye problems at a younger age than usual, such as cataracts (clouding of the eye's lens) and glaucoma (increased pressure inside the eye), which can further affect their sight. Because ADVIRC can affect vision in multiple ways, it is important for patients to have regular, comprehensive eye exams. While there is currently no cure for the underlying genetic cause, many of the complications can be treated. For example, glasses can help with far-sightedness, and surgery or medications can be used to manage cataracts and glaucoma. Monitoring the retina is also crucial so that any swelling or abnormal blood vessel growth can be treated promptly to help preserve vision for as long as possible.

Symptoms and clinical features: Symptoms of ADVIRC vary significantly among affected individuals. In the early stages, patients may be asymptomatic or experience mild visual disturbances. Due to the developmental anomalies, patients often present with hyperopia (farsightedness) and may have noticeably smaller corneas (microcornea). As the disease progresses, symptoms related to complications arise. Patients may experience blurred or decreased central vision if cataracts or macular edema develop. The presence of a shallow anterior chamber puts patients at risk for acute angle-closure glaucoma, which can present with sudden eye pain, redness, halos around lights, and severe vision loss. Some patients may notice floaters due to vitreous degeneration or sudden vision changes if a vitreous hemorrhage occurs from choroidal neovascularization. Night blindness is generally not a prominent early feature but peripheral vision may slowly constrict over time.

Molecular pathology: Autosomal dominant vitreoretinochoroidopathy (ADVIRC) is caused by heterozygous mutations in the BEST1 gene, located on chromosome 11q12.3. The BEST1 gene encodes bestrophin-1, a 68 kDa transmembrane protein that localizes predominantly to the basolateral plasma membrane of the retinal pigment epithelium (RPE). Bestrophin-1 functions as a calcium-activated chloride channel and is also involved in the transport of other large anions, such as bicarbonate. Additionally, it interacts with and modulates intracellular voltage-dependent calcium channels, playing a crucial role in maintaining the ionic balance and fluid homeostasis in the subretinal space, which is essential for normal RPE and photoreceptor function. The mutations associated with ADVIRC are distinct from those causing other bestrophinopathies like Best vitelliform macular dystrophy. ADVIRC is primarily linked to specific missense mutations (e.g., p.Val86Met, p.Val239Met, p.Tyr236Cys, p.Val235Ala, and p.Gly83Asp) and variants that alter pre-mRNA splicing, leading to in-frame deletions or duplications. These specific alterations are thought to affect the first restriction site and the calcium-clasp site of the bestrophin-1 ion channel. The exact pathophysiological mechanism of ADVIRC remains partially understood. It is hypothesized that these specific BEST1 mutations lead to altered anion permeability and disrupted calcium homeostasis in the RPE. Unlike other bestrophinopathies that primarily affect the macula, ADVIRC mutations seem to have a more profound effect on the peripheral RPE and are uniquely associated with ocular developmental anomalies. The disruption of RPE function may alter the regulation of growth factor signaling to the choroid and sclera during eye development, leading to the pan-ophthalmic features characteristic of ADVIRC, such as microcornea and nanophthalmos, alongside the progressive vitreoretinal degeneration.

Genetics: Autosomal dominant vitreoretinochoroidopathy (ADVIRC) is inherited in an autosomal dominant manner. This means that a single copy of the altered BEST1 gene in each cell is sufficient to cause the disorder. In most cases, an affected individual inherits the mutation from one affected parent. Each child of an affected individual has a 50% chance of inheriting the pathogenic variant and developing the condition. The BEST1 gene, located on chromosome 11q12.3, encodes the bestrophin-1 protein. ADVIRC is specifically associated with certain missense mutations (such as p.Val86Met, p.Val239Met, p.Tyr236Cys, p.Val235Ala, and p.Gly83Asp) and splice-site variants that lead to in-frame deletions or duplications. These mutations are thought to alter the pre-mRNA splicing or affect the channel properties of the bestrophin-1 protein. The condition exhibits variable expressivity, meaning that the severity and specific signs and symptoms can vary significantly even among affected members of the same family. While penetrance appears to be high, the clinical presentation can range from mild peripheral retinal changes with normal vision to severe visual impairment due to complications like glaucoma, cataracts, or macular involvement. Genetic counseling is recommended for affected individuals and their families to discuss the risks, inheritance pattern, and available testing options, including prenatal and preimplantation genetic testing.

Diagnostic evaluation: Diagnosis of ADVIRC is based on clinical findings, electrophysiological testing, and molecular genetic testing. Clinical examination typically reveals a characteristic circumferential band of hyperpigmentation in the peripheral retina with a distinct posterior boundary, often accompanied by white punctate opacities. Anterior segment evaluation may show microcornea, shallow anterior chamber, and signs of angle-closure glaucoma. Electrophysiological testing is crucial; the electrooculogram (EOG) is characteristically abnormal with a reduced Arden ratio (light peak to dark trough ratio < 1.5), while the full-field electroretinogram (ERG) may be normal initially but can show reduced rod and cone responses as the disease progresses. Optical coherence tomography (OCT) is used to assess macular involvement, such as cystoid macular edema or thinning, and to monitor fluid accumulation. Fundus autofluorescence typically shows normal central fluorescence with blocked fluorescence in the periphery corresponding to the hyperpigmented band. The diagnosis is confirmed by identifying a heterozygous pathogenic variant in the BEST1 gene, typically involving specific missense mutations or splice-site alterations (e.g., p.V86M, p.V239M) that affect the bestrophin-1 protein.

Differential diagnosis: Best vitelliform macular dystrophy, Adult-onset vitelliform macular dystrophy, Autosomal recessive bestrophinopathy, Retinitis pigmentosa, Microcornea-rod-cone dystrophy-cataract-posterior staphyloma (MRCS) syndrome

Natural history: The natural history of ADVIRC is characterized by a slow, progressive vitreoretinal degeneration combined with developmental ocular anomalies. The disease typically manifests in the first decade of life, often with the presence of the characteristic peripheral retinal hyperpigmented band and developmental features like microcornea or hyperopia. In the early stages, central vision is usually preserved, and patients may be asymptomatic or present with mild visual disturbances. As the patient progresses into their twenties and thirties, vision generally remains stable, but complications such as early-onset cataracts and angle-closure glaucoma may develop due to the crowded anterior segment. The vitreous may show fibrillar condensation and liquefaction. Over time, the peripheral chorioretinal atrophy can slowly advance. In later stages, typically after the fourth or fifth decade, patients may experience a decline in central vision. This can be due to the development of cystoid macular edema, epiretinal membranes, or chorioretinal macular atrophy. Choroidal neovascularization can also occur, leading to sudden visual loss from hemorrhage. While progression is generally slow, some patients may experience a more rapid decline in vision, and the severity of the disease can vary widely even within the same family.

Management and treatment research: Currently, there is no cure or specific medical treatment to halt or reverse the underlying genetic defect in ADVIRC. Management is primarily symptomatic and focuses on treating the associated complications to preserve vision. Regular, comprehensive ophthalmic monitoring is essential. For anterior segment complications, hyperopia is managed with corrective lenses. The risk of angle-closure glaucoma due to a crowded anterior segment is a major concern; prophylactic laser peripheral iridotomy may be considered, and if glaucoma develops, it is treated with intraocular pressure-lowering medications, laser therapy, or glaucoma filtration surgery. Early-onset cataracts are managed with surgical extraction, though the procedure can be complex due to the small eye size (nanophthalmos) and shallow anterior chamber. Posterior segment complications also require targeted therapies. Cystoid macular edema can be treated with topical or intravitreal corticosteroids, or intravitreal anti-VEGF (vascular endothelial growth factor) injections. If choroidal neovascularization occurs, anti-VEGF therapy is the standard of care to prevent severe vision loss from hemorrhage and scarring. Retinal breaks or detachments, though less common, require prompt surgical repair. While gene therapy and stem cell treatments are being actively researched for other inherited retinal diseases and bestrophinopathies, there are currently no specific pipeline therapies or clinical trials exclusively targeting ADVIRC.

Outlook: The visual prognosis for patients with ADVIRC is highly variable due to the condition's variable expressivity. Many patients maintain good central vision (20/40 or better) well into adulthood, as the disease primarily affects the peripheral retina in its early stages. However, vision can slowly decline with age. The long-term visual outcome is heavily dependent on the management of associated complications. Severe visual impairment or blindness can occur if complications such as angle-closure glaucoma, early-onset cataracts, cystoid macular edema, or choroidal neovascularization are not promptly diagnosed and treated. With appropriate and proactive ophthalmic care, many patients can retain functional vision for a significant portion of their lives, though quality of life may be impacted by the need for ongoing monitoring and interventions.

Epidemiology: Autosomal dominant vitreoretinochoroidopathy (ADVIRC) is an extremely rare genetic disorder. It is considered an ultra-rare disease, with its exact prevalence remaining unknown, though it is estimated to affect less than 1 in 1,000,000 individuals worldwide. The condition has been reported in a limited number of families globally since its first description in 1982. There is no known ethnic or geographic predilection, and it affects males and females equally due to its autosomal dominant inheritance pattern. The disease typically presents in the first decade of life, though the age of diagnosis can vary depending on the severity of symptoms and the presence of anterior segment complications such as glaucoma or cataracts.

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