Exudative Vitreoretinopathy 1

A number sign (#) is used with this entry because familial exudative vitreoretinopathy-1 (EVR1) is caused by heterozygous mutation in the frizzled-4 gene (FZD4; 604579) on chromosome 11q14.

A form of retinopathy of prematurity is also caused by mutation in the FZD4 gene.

Description

Familial exudative vitreoretinopathy (FEVR) is an inherited disorder characterized by the incomplete development of the retinal vasculature. Its clinical appearance varies considerably, even within families, with severely affected patients often registered as blind during infancy, whereas mildly affected patients with few or no visual problems may have such a small area of avascularity in their peripheral retina that it is visible only by fluorescein angiography. It is believed that this peripheral avascularity is the primary anomaly in FEVR and results from defective retinal angiogenesis. The sight-threatening features of the FEVR phenotype are considered secondary to retinal avascularity and develop because of the resulting retinal ischemia; they include the development of hyperpermeable blood vessels, neovascularization, vitreoretinal traction, retinal folds, and retinal detachments (summary by Poulter et al., 2010).

In 31 Chinese pedigrees clinically diagnosed with FEVR, Rao et al. (2017) analyzed 6 FEVR-associated genes and identified mutations in 12 of the probands, including 5 (16.1%) in LRP5, 3 (9.7%) in NDP, 2 (6.5%) in FZD4, and 1 (3.2%) in TSPAN12. In addition, a mutation in the KIF11 gene (148760) was identified in a patient who also exhibited microcephaly (MCLMR; 152950). The authors noted that their detection rate did not exceed 50%, suggesting that other FEVR-associated genes remained to be discovered.

Genetic Heterogeneity of Familial Exudative Vitreoretinopathy

Also see EVR2 (305390), caused by mutation in the NDP gene (300658) on chromosome Xp11; EVR3 (605750), mapped to 11p13-p12; EVR4 (601813), caused by mutations in the LRP5 gene (603506) on 11q13.4; EVR5 (613310), caused by mutation in the TSPAN12 gene (613138) on 7q31; EVR6 (616468), caused by mutation in the ZNF408 gene (616454) on 11p11; and EVR7 (617572), caused by mutation in the CTNNB1 gene (116806) on chromosome 3p22.

Clinical Features

Familial exudative vitreoretinopathy was first described by Criswick and Schepens (1969) on the basis of 6 patients in 2 kindreds. The findings bore some similarities to retrolental fibroplasia and to Coats disease (see 300216). The changes were slowly progressive. Affected children were otherwise healthy. None was premature or treated neonatally with oxygen. Posterior vitreous detachment with organized membranes were found in all quadrants. Vitreoretinal traction was produced by membranes and resulted in displacement of the macula. Snowflake opacities were scattered through the vitreous humor. Localized retinal detachment and displacements and recurrent vitreous hemorrhages from peripheral new vessels were noted. A brother and sister in 1 family were affected. In the other family, 3 brothers and their maternal uncle were affected. A distant male relative related through females was blind, making X-linked recessive inheritance a possibility. This may be the same as congenital falciform retinal detachment (221900).

Gow and Oliver (1971) added another series of cases from an extensively affected kindred. Canny and Oliver (1976) divided the clinical course into 3 stages on the basis of studies of Gow and Oliver's pedigree, which in its updated form showed proved or probable cases in 6 successive generations. Under the designation of peripheral retinal neovascularization, Gitter et al. (1978) probably described the same disorder. Nine members of the family showed wide variability in severity and slow progression. Some eyes progressed to vitreous hemorrhage, secondary cataract, and phthisis bulbi. Two other affected members of the family progressed to total retinal detachment. Penetrance is about 100%, but many patients have very mild disease that is detectable with certainty only by fluorescein angiography (Ober et al., 1980). Progression of fundus changes and threat to vision is rare after age 20 years.

The similarity to retinopathy of prematurity (ROP) or retrolental fibroplasia can be striking (Slusher and Hutton, 1979). In studies of a large Dutch kindred, Nijhuis et al. (1979) found fluorescein angiography indispensable in demonstrating the earliest detectable abnormalities of the disorder and in distinguishing affected from unaffected persons.

In studies of a large German kindred, Laqua (1980) concluded that FEVR is inherited as an autosomal dominant and is a disease primarily of small peripheral vessels leading to fibrovascular mass lesions. Miyakubo et al. (1982) identified 30 cases in 11 families as well as 4 sporadic cases, all male. In 8 affected members of a family, Feldman et al. (1983) described clinical findings including retinal detachment, fibrovascular masses with dragged disc and macula, neovascular fronds, and intraretinal deposits. Miyakubo et al. (1984) proposed a grading system into 5 types. In the Netherlands, van Nouhuys (1989) observed retinal detachment in 36 (20%) of 180 eyes of 90 persons with FEVR from 17 families. He pointed out that FEVR can give rise to very different types of retinal detachment, such as rhegmatogenous retinal detachment, falciform retinal folds, and exudative retinal detachment. All but one retinal detachment occurred before the age of 30. Traction from vitreous membranes seemed to be the most important cause of retinal detachment; atrophy of the peripheral retina may contribute to the formation of retinal breaks. In 4 eyes of 3 patients from 2 large families with FEVR, van Nouhuys (1981) found congenital retinal fold (ablatio falciformis congenita), which, he suggested, should be considered a sign rather than a diagnosis. The formation of congenital retinal fold is the consequence of a developmental disorder of retinal vasculature during the last few months of intrauterine life and the folds may even develop after birth. The clinical picture and familial occurrence of many cases of congenital retinal fold previously described were suggestive of dominant exudative vitreoretinopathy, which is a rather common disorder. Nishimura et al. (1983) likewise found falciform retinal fold as a sign of FEVR. Ida Mann (1935), writing about congenital retinal fold, suggested that this 'curious and striking congenital abnormality...is not so rare as the paucity of the literature concerning it would suggest.'

Familial exudative vitreoretinopathy 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 legally blind during the first decade of life, whereas mildly affected individuals may not be aware of symptoms and may receive a diagnosis only by use of fluorescein angiography. The primary pathologic 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. This failure to vascularize the peripheral retina is the unifying feature seen in all affected individuals, but, by itself, it usually causes no clinical symptoms. The visual problems in FEVR result from secondary complications due to the development of hyperpermeable blood vessels, neovascularization, and vitreoretinal traction. These features cause a reduction in visual acuity and, in 20% of cases, can lead to partial or total retinal detachment (van Nouhuys, 1991).

Ranchod et al. (2011) described the clinical characteristics, staging, and presentation of patients with FEVR in their clinical practice over the foregoing 25 years. They included 273 eyes of 145 patients. Patients were slightly male-predominant (57%) with a mean birth weight of 2.80 kg (range, 740 g-4.76 kg), mean gestational age of 37.8 weeks (range, 25-42) and mean age at presentation of almost 6 years (range, less than 1 month-49 years). A positive family history of FEVR was obtained in 18% of patients. A positive family history of ocular disease consistent with but not diagnosed as FEVR was obtained in an additional 19%. Stage 1 FEVR was identified in 45 eyes, stage 2 in 33 eyes, stage 3 in 42 eyes, stage 4 in 89 eyes, and stage 5 in 44 eyes. Radial retinal folds were seen in 77 eyes, which in 64 were temporal or inferotemporal in location. While the majority of retinal folds extended radially in the temporal quadrants, radial folds were seen in almost all quadrants. Fellow eyes demonstrated a wide variation in symmetry. Ranchod et al. (2011) concluded that the presentation of FEVR might mimic the presentation of other pediatric and adult vitreoretinal disorders, and careful examination is often crucial in making the diagnosis of FEVR.

Other Features

Fulton et al. (2001) studied the electroretinographic (ERG) responses in 25 children characterized by maximum, acute phase retinopathy of prematurity (ROP) ranging from 'none' to 'very severe.' In the none to severe categories, the ERG responses varied significantly with the severity of acute phase ROP. In the very severe category, the ERG responses were too attenuated to calculate the responses. The authors concluded that rod photoreceptors must be involved in ROP. They found that the more severe the acute phase ROP, the more severe the compromise of the processes involved in the activation of phototransduction in the rods.

Diagnosis

Differential Diagnosis

Robitaille et al. (2014) found phenotypic overlap between FEVR and microcephaly with or without chorioretinopathy, lymphedema, or mental retardation (MCLMR; 152950). In 4 of 28 probands with a diagnosis of FEVR made by the referring physician and without a known FEVR gene mutation, the authors identified heterozygous mutations in the KIF11 gene (see, e.g., 148760.0009 and 148760.0010). At least 1 patient in each pedigree manifested 1 or more of the following features: macular dragging, partial retinal detachment, falciform folds, or total retinal detachment, typical of FEVR. Three of the probands had microcephaly; the fourth was lost to follow-up. Robitaille et al. (2014) recommended that children presenting with partial or complete retinal detachments at a young age be examined for mild to moderate microcephaly, which could lead to a more precise diagnosis and accurate genetic counseling.

Mapping

Li et al. (1992) found a suggestion of linkage to markers on 11q: with INT2 (164950) at 11q13 and D11S35 at 11q22-q23, they found peak lod scores of 2.36 and 2.32, respectively, at recombination fractions of 0.10 and 0.07, respectively. They detected about 15% recombination between the 2 markers and concluded that the EVR locus may lie between the 2 markers, with INT2 toward the centromere. Li et al. (1992) found the highest 2-point lod score (3.67, at a recombination fraction of 0.07) for the disease locus versus D11S533. Multipoint analysis showed that the EVR locus most likely maps, with a maximum lod score of over 20, between D11S533/D11S527 and D11S35, at recombination rates of 0.147 and 0.104, respectively. Close linkage without recombination (maximum lod score = 11.26) had been found between D11S533 and D11S527. As reviewed by Muller et al. (1994), 2-point linkage analysis on a total of 4 families had demonstrated close linkage of EVR1 to D11S873; maximum lod = 8.34 at theta = 0.00. Multipoint linkage analysis mapped the EVR1 locus between D11S527/D11S533 and D11S35 with a maximum lod score of over 11 directly at D11S873. There was no evidence of genetic linkage heterogeneity among the 4 families studied.

The VMD2 gene (BEST1; 607854), the causative gene for other forms of macular dystrophy, including vitelliform macular dystrophy (153700), maps to approximately the same area. Although these are apparently separate entities caused by mutations in separate genes, those genes may be in a cluster reflecting a common ancestry.

Molecular Genetics

In affected members of families with the form of FEVR mapping to 11q13-q23, EVR1, Robitaille et al. (2002) identified mutations in the FZD4 gene (604579.0001-604579.0002).

Kondo et al. (2003), Yoshida et al. (2004), and Qin et al. (2005) identified heterozygous mutations in the FZD4 gene (see, e.g., 604579.0003-604579.0005) in Japanese patients with EVR1. Some asymptomatic parents who carried the mutations showed peripheral retinal avascularization.

Qin et al. (2005) reported a Japanese family with digenic inheritance of EVR. Affected individuals had a heterozygous mutation in the FZD4 gene (604579.0003) and a heterozygous mutation in the LRP5 gene (603506.0026).

Of 68 probands diagnosed as having autosomal dominant or sporadic FEVR, Robitaille et al. (2011) identified 11 different FZD4 mutations (5 missense, 3 deletions, 1 insertion, 2 nonsense) in 12 probands. Six of these mutations were novel, and none were found in 346 control chromosomes.

Retinopathy of Prematurity

In an infant with advanced retinopathy of prematurity, MacDonald et al. (2005) identified heterozygosity for a mutation in the FZD4 gene (604579.0006).