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Cone rod dystrophies.

Hamel CP - Orphanet J Rare Dis (2007)

Bottom Line: At end stage, however, CRDs do not differ from RCDs.Currently, there is no therapy that stops the evolution of the disease or restores the vision, and the visual prognosis is poor.Management aims at slowing down the degenerative process, treating the complications and helping patients to cope with the social and psychological impact of blindness.

View Article: PubMed Central - HTML - PubMed

Affiliation: Inserm U. 583, Physiopathologie et thérapie des déficits sensoriels et moteurs, Institut des Neurosciences de Montpellier, BP 74103, 80 av, Augustin Fliche, 34091 Montpellier Cedex 05, France. hamel@montp.inserm.fr

ABSTRACT
Cone rod dystrophies (CRDs) (prevalence 1/40,000) are inherited retinal dystrophies that belong to the group of pigmentary retinopathies. CRDs are characterized by retinal pigment deposits visible on fundus examination, predominantly localized to the macular region. In contrast to typical retinitis pigmentosa (RP), also called the rod cone dystrophies (RCDs) resulting from the primary loss in rod photoreceptors and later followed by the secondary loss in cone photoreceptors, CRDs reflect the opposite sequence of events. CRD is characterized by primary cone involvement, or, sometimes, by concomitant loss of both cones and rods that explains the predominant symptoms of CRDs: decreased visual acuity, color vision defects, photoaversion and decreased sensitivity in the central visual field, later followed by progressive loss in peripheral vision and night blindness. The clinical course of CRDs is generally more severe and rapid than that of RCDs, leading to earlier legal blindness and disability. At end stage, however, CRDs do not differ from RCDs. CRDs are most frequently non syndromic, but they may also be part of several syndromes, such as Bardet Biedl syndrome and Spinocerebellar Ataxia Type 7 (SCA7). Non syndromic CRDs are genetically heterogeneous (ten cloned genes and three loci have been identified so far). The four major causative genes involved in the pathogenesis of CRDs are ABCA4 (which causes Stargardt disease and also 30 to 60% of autosomal recessive CRDs), CRX and GUCY2D (which are responsible for many reported cases of autosomal dominant CRDs), and RPGR (which causes about 2/3 of X-linked RP and also an undetermined percentage of X-linked CRDs). It is likely that highly deleterious mutations in genes that otherwise cause RP or macular dystrophy may also lead to CRDs. The diagnosis of CRDs is based on clinical history, fundus examination and electroretinogram. Molecular diagnosis can be made for some genes, genetic counseling is always advised. Currently, there is no therapy that stops the evolution of the disease or restores the vision, and the visual prognosis is poor. Management aims at slowing down the degenerative process, treating the complications and helping patients to cope with the social and psychological impact of blindness.

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Fundus of a 31 year-old patient with Bardet Biedl syndrome. The peripheral retina does not show any large lesion but the macula is atrophic.
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Figure 2: Fundus of a 31 year-old patient with Bardet Biedl syndrome. The peripheral retina does not show any large lesion but the macula is atrophic.

Mentions: • Bardet Biedl syndrome (BBS) is an autosomal recessive disease with a prevalence ranging from 1/13,500 to 1/60,000. It associates retinal dystrophy with postaxial polydactyly, obesity, hypogenitalism, mental retardation or mild psychomotor delay, and renal abnormalities that can lead to renal failure. The retinal dystrophy is classically described as a RCD but many variants have been reported with a prominent macular involvement (Figure 2), indicating a CRD [2]. In fact, BBS patients have the diffuse type of CRD. In our experience, they always have macular involvement, with decreased visual acuity, photophobia and foveomacular hyperfluorescence on fluorescein angiography. The diagnosis of retinal dystrophy is often established in the first decade of life and legal blindness is reached before 20 years of age, but there are moderate forms of the disease. Diagnosis may be difficult when the clinical picture is incomplete. In this case, the presence of a CRD is an important sign. Twelve BBS genes encoding proteins involved in the cilium structure have been reported so far.


Cone rod dystrophies.

Hamel CP - Orphanet J Rare Dis (2007)

Fundus of a 31 year-old patient with Bardet Biedl syndrome. The peripheral retina does not show any large lesion but the macula is atrophic.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1808442&req=5

Figure 2: Fundus of a 31 year-old patient with Bardet Biedl syndrome. The peripheral retina does not show any large lesion but the macula is atrophic.
Mentions: • Bardet Biedl syndrome (BBS) is an autosomal recessive disease with a prevalence ranging from 1/13,500 to 1/60,000. It associates retinal dystrophy with postaxial polydactyly, obesity, hypogenitalism, mental retardation or mild psychomotor delay, and renal abnormalities that can lead to renal failure. The retinal dystrophy is classically described as a RCD but many variants have been reported with a prominent macular involvement (Figure 2), indicating a CRD [2]. In fact, BBS patients have the diffuse type of CRD. In our experience, they always have macular involvement, with decreased visual acuity, photophobia and foveomacular hyperfluorescence on fluorescein angiography. The diagnosis of retinal dystrophy is often established in the first decade of life and legal blindness is reached before 20 years of age, but there are moderate forms of the disease. Diagnosis may be difficult when the clinical picture is incomplete. In this case, the presence of a CRD is an important sign. Twelve BBS genes encoding proteins involved in the cilium structure have been reported so far.

Bottom Line: At end stage, however, CRDs do not differ from RCDs.Currently, there is no therapy that stops the evolution of the disease or restores the vision, and the visual prognosis is poor.Management aims at slowing down the degenerative process, treating the complications and helping patients to cope with the social and psychological impact of blindness.

View Article: PubMed Central - HTML - PubMed

Affiliation: Inserm U. 583, Physiopathologie et thérapie des déficits sensoriels et moteurs, Institut des Neurosciences de Montpellier, BP 74103, 80 av, Augustin Fliche, 34091 Montpellier Cedex 05, France. hamel@montp.inserm.fr

ABSTRACT
Cone rod dystrophies (CRDs) (prevalence 1/40,000) are inherited retinal dystrophies that belong to the group of pigmentary retinopathies. CRDs are characterized by retinal pigment deposits visible on fundus examination, predominantly localized to the macular region. In contrast to typical retinitis pigmentosa (RP), also called the rod cone dystrophies (RCDs) resulting from the primary loss in rod photoreceptors and later followed by the secondary loss in cone photoreceptors, CRDs reflect the opposite sequence of events. CRD is characterized by primary cone involvement, or, sometimes, by concomitant loss of both cones and rods that explains the predominant symptoms of CRDs: decreased visual acuity, color vision defects, photoaversion and decreased sensitivity in the central visual field, later followed by progressive loss in peripheral vision and night blindness. The clinical course of CRDs is generally more severe and rapid than that of RCDs, leading to earlier legal blindness and disability. At end stage, however, CRDs do not differ from RCDs. CRDs are most frequently non syndromic, but they may also be part of several syndromes, such as Bardet Biedl syndrome and Spinocerebellar Ataxia Type 7 (SCA7). Non syndromic CRDs are genetically heterogeneous (ten cloned genes and three loci have been identified so far). The four major causative genes involved in the pathogenesis of CRDs are ABCA4 (which causes Stargardt disease and also 30 to 60% of autosomal recessive CRDs), CRX and GUCY2D (which are responsible for many reported cases of autosomal dominant CRDs), and RPGR (which causes about 2/3 of X-linked RP and also an undetermined percentage of X-linked CRDs). It is likely that highly deleterious mutations in genes that otherwise cause RP or macular dystrophy may also lead to CRDs. The diagnosis of CRDs is based on clinical history, fundus examination and electroretinogram. Molecular diagnosis can be made for some genes, genetic counseling is always advised. Currently, there is no therapy that stops the evolution of the disease or restores the vision, and the visual prognosis is poor. Management aims at slowing down the degenerative process, treating the complications and helping patients to cope with the social and psychological impact of blindness.

Show MeSH
Related in: MedlinePlus