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PubMed1983

Retinitis pigmentosa--an overview.

Retinitis pigmentosa is a retinal pigment dystrophy of multiple genetic inheritance patterns affecting approximately .5% of the world population. It may be recognized clinically by observing specific ophthalmoscopic changes, as well as through psychophysical and electrodiagnostic testing. It may also be associated with several other genetic conditions. Basic research indicates that while there is no specific cure, certain precautions may prevent rapid acceleration of the disease process. This article presents an overview of retinitis pigmentosa, including its diagnosis and genetic patterns, and discusses various auxiliary aids and filters that may be helpful in protecting and increasing visual function in R.P. patients.

Child↗
PubMed1998

Retinitis pigmentosa inversa.

BACKGROUND: Retinitis pigmentosa (RP) is one of the most common inherited retinal diseases, with a prevalence of about 1 in 3500 to 4500. Retinitis pigmentosa inversa is a rare variant of this disorder characterized by areas of choroidal degeneration with pigment migration and bony spicule formation in the macular area. In contrast to more typical forms of RP, this anomaly destroys central vision, leaving peripheral vision intact. CASE REPORT: A 47-year-old white male was followed for about 7 years with evidence of progressive retinal pigment epithelial atrophy and hyperpigmentation affecting both maculae. Since 1970, he had noted difficulty seeing at night as well as an acquired hearing deficit that appeared to be getting worse, ultimately impairing his ability to safely drive a truck. Medical history was positive for either chloroquine or hydroxychloroquine use for 2 to 3 years as malaria prophylaxis while he served in Vietnam. In addition, his father in Louisiana had visual loss of unknown cause. During the 7-year period, the condition progressed rapidly. The patient became virtually blind secondary to visual acuity loss with dense central and paracentral scotomas. The peripheral visual fields remained intact. After several years of extensive examinations, including laboratory, electroretinography, and genetic testing, a definitive diagnosis of RP inversa was made. DISCUSSION: RP inversa is a rare form of tapetoretinal degeneration that is characterized by decreased central vision with normal peripheral vision. A recessive form of inheritance has been postulated but never substantiated. Although there is currently no treatment, recent studies have indicated that 15,000 IU of vitamin A palmitate daily may slow the progression of retinitis pigmentosa; however, it is unknown whether this treatment would be effective for the inverse form of RP. Differential diagnoses include Leber's congenital amaurosis, central gyrate atrophy, central areolar choroidal sclerosis, progressive cone-rod dystrophy, syphilitic retinopathy, retinal toxicity from phenothiazine use, and chloroquine/hydroxychloroquine retinopathy.

Adult↗
PubMed1987

Retinitis pigmentosa with segmental massive retinal gliosis. An immunohistochemical, biochemical, and ultrastructural study.

A morphologic, immunohistologic, and biochemical study was made on the eyes of a 79-year-old woman with clinically documented retinitis pigmentosa (RP). The methods included light and electron microscopy, immunohistologic staining, and biochemical analysis of interphotoreceptor retinoid-binding protein (IRBP) and cyclic nucleotides. Results from a histopathologic examination showed marked equatorial pigmentary retinal degeneration as well as peripheral chorioretinal atrophy corresponding to areas of paving stone chorioretinal changes. An unusual finding was a localized equatorial nodule in the right eye that stained with anti-glial fibrillary acidic protein (GFAP) antibodies, and showed lipid infiltrates in its margin and base. The equatorial retina showed marked gliosis of the outer layers. Photoreceptor cells were present only in the posterior retina, macula, and focally, in the far periphery. These areas corresponded to detectable IRBP assessed by immunohistochemical staining and biochemical analysis using the enzyme-linked immunosorbent assay (ELISA). Cyclic nucleotides were reduced in the peripheral retina, in areas of photoreceptor cell loss.

Aged↗
PubMed1998

Histopathology of the human retina in retinitis pigmentosa.

The term, 'retinitis pigmentosa', refers to a heterogeneous group of inherited diseases that cause degeneration of rod and cone photoreceptors in the human retina. Loss of photoreceptor cells is usually followed by alterations in the retinal pigment epithelium and retinal glia. Ultimately, degenerative changes occur in the inner retinal neurons, blood vessels, and optic nerve head. This chapter provides background information on the genetics of retinitis pigmentosa and a summary of the histopathologic alterations in human retinas caused by this disease. Detailed information is provided on the effects of the primary disease process on the rod photoreceptors and changes in the other retinal components, all of which are important considerations for understanding and developing therapies for retinitis pigmentosa.

Astrocytes↗
PubMed2002

Mutations in the inosine monophosphate dehydrogenase 1 gene (IMPDH1) cause the RP10 form of autosomal dominant retinitis pigmentosa.

Autosomal dominant retinitis pigmentosa (adRP) is a heterogeneous set of progressive retinopathies caused by several distinct genes. One locus, the RP10 form of adRP, maps to human chromosome 7q31.1 and may account for 5-10% of adRP cases among Americans and Europeans. We identified two American families with the RP10 form of adRP by linkage mapping and used these families to reduce the linkage interval to 3.45 Mb between the flanking markers D7S686 and RP-STR8. Sequence and transcript analysis identified 54 independent genes within this region, at least 10 of which are retinal-expressed and thus candidates for the RP10 gene. A screen of retinal transcripts comparing retinas from normal mice to retinas from crx-/crx- knockout mice (with poorly differentiated photoreceptors) demonstrated a 6-fold reduction in one candidate, inosine monophosphate dehydrogenase 1 (IMPDH1; EC 1.1.1.205). Since many of the genes known to cause retinitis pigmentosa are under CRX control in photoreceptors, IMPDH1 became a high-priority candidate for mutation screening. DNA sequencing of affected individuals from the two American RP10 families revealed a GAC-->AAC transition in codon 226 substituting an asparagine for an aspartic acid in both families. The identical mutation was also found in a British RP10 family. The Asp226Asn missense mutation is present in all affected individuals tested and absent from unaffected controls. The aspartic acid at codon 226 is conserved in all IMPDH genes, in all species examined, including bacteria, suggesting that this mutation is highly deleterious. Subsequent screening of probands from 60 other adRP families revealed an additional family with this mutation, confirming its association with retinitis pigmentosa and the relatively high frequency of this mutation. Another IMPDH1 substitution, Val268Ile, was also observed in this cohort of patients but not in controls. IMPDH1 is a ubiquitously expressed enzyme, functioning as a homotetramer, which catalyzed the rate-limiting step in de novo synthesis of guanine nucleotides. As such, it plays an important role in cyclic nucleoside metabolism within photoreceptors. Several classes of drugs are known to affect IMPDH isoenzymes, including nucleotide and NAD analogs, suggesting that small-molecule therapy may be available, one day, for RP10 patients.

Amino Acid Motifs↗
PubMed1988

The relation of rhodopsin and scotopic retinal sensitivity in sector retinitis pigmentosa.

We used reflection retinal densitometric, psychophysical, and electroretinographic techniques to study the scotopic retinal function of a mother and her three daughters who had clinical evidence of a sectoral type of retinitis pigmentosa. Retinal regions with, and those without, ophthalmoscopic signs of degeneration were investigated. During dark adaptation, the time courses of rhodopsin regeneration and recovery of scotopic sensitivity were similar to normal as was the relation of rhodopsin to scotopic threshold. In dark-adapted eyes, threshold increases were not proportional to rhodopsin loss. The results of psychophysical tests of background adaptation and temporal summation, and analysis of the relation of electroretinographic a- to b-wave amplitudes, led to the conclusion that abnormalities of photoreceptor cell function central to the rhodopsin-bearing outer segments accounted for the increased thresholds.

Adult↗
PubMed1994

Structure and function in rhodopsin. 7. Point mutations associated with autosomal dominant retinitis pigmentosa.

Autosomal dominant retinitis pigmentosa (ADRP) is a hereditary form of retinitis pigmentosa which accounts for about 15% of all types of the latter disease. Recently, close to 50 mutations, mostly point mutations, have been identified in the rhodopsin gene in ADRP patients. We have introduced these mutations in the synthetic bovine rhodopsin gene and herein report on the expression of the mutant genes in COS-1 cells and studies in vitro of the properties of the expressed opsins. The mutant phenotypes fall into three classes: Class I mutants are expressed in COS-1 cells at wild-type levels, form the normal rhodopsin chromophore with 11-cis-retinal, and are transported to the cell surface. However, on illumination, they activate transducin inefficiently. Class II mutants remain in the endoplasmic reticulum and do not bind 11-cis-retinal to form the chromophore. Class III mutants are expressed at low levels and form rhodopsin chromophore only poorly. They also remain in the endoplasmic reticulum and, as expected, show high mannose glycosylation. Nearly all of the mutants studied show abnormal sensitivity to light compared to the wild type, and they activate transducin less efficiently. We conclude that the majority of the ADRP mutants have folding defects.

Amino Acid Sequence↗
PubMed1999

Mutation analysis of the RPGR gene reveals novel mutations in south European patients with X-linked retinitis pigmentosa.

The RPGR (retinitis pigmentosa GTPase regulator) gene has been shown to be mutated in 10-20% of patients with X-linked retinitis pigmentosa (XLRP), a severe form of inherited progressive retinal degeneration. A total of 29 different RPGR mutations have been identified in northern European and United States patients. We have performed mutation analysis of the RPGR gene in a cohort of 49 southern European males affected with XLRP. By multiplex SSCA and automatic direct sequencing of all 19 RPGR exons, seven different and novel mutations were identified in eight of the 49 families; these include three splice site mutations, two microdeletions, and two missense mutations. RNA analysis showed that the three splice site defects resulted in the generation of aberrant RPGR transcripts. Six of these mutations were detected in the conserved amino-terminal region of RPGR protein, containing tandem repeats homologous to the RCC1 protein, a guanine nucleotide-exchange factor for Ran-GTPase. Several exonic and intronic sequence variations were also detected. None of the RPGR mutations reported in other populations were identified in our series. Our results are consistent with the notions of heterogeneity and minority causation of XLRP by mutations in RPGR in Caucasian populations.

Base Sequence↗
PubMed1997

Spectrum of mutations in the RPGR gene that are identified in 20% of families with X-linked retinitis pigmentosa.

The RPGR (retinitis pigmentosa GTPase regulator) gene for RP3, the most frequent genetic subtype of X-linked retinitis pigmentosa (XLRP), has been shown to be mutated in 10%-15% of European XLRP patients. We have examined the RPGR gene for mutations in a cohort of 80 affected males from apparently unrelated XLRP families, by direct sequencing of the PCR-amplified products from the genomic DNA. Fifteen different putative disease-causing mutations were identified in 17 of the 80 families; these include four nonsense mutations, one missense mutation, six microdeletions, and four intronic-sequence substitutions resulting in splice defects. Most of the mutations were detected in the conserved N-terminal region of the RPGR protein, containing tandem repeats homologous to those present in the RCC-1 protein (a guanine nucleotide-exchange factor for Ran-GTPase). Our results indicate that mutations either in as yet uncharacterized sequences of the RPGR gene or in another gene located in its vicinity may be a more frequent cause of XLRP. The reported studies will be beneficial in establishing genotype-phenotype correlations and should lead to further investigations seeking to understand the mechanism of disease pathogenesis.

Carrier Proteins↗
PubMed1980

Low vision correction in retinitis pigmentosa and associated diseases.

Retinitis pigmentosa was considered unfavorable for low vision corrections before it was recognized that the term retinitis pigmentosa as frequently used referred to a group of disease entities including Leber's congenital amaurosis, centro-peripheral dystrophy, typical retinitis pigmentosa and Usher's syndrome. The success rate for use of optical aids was Leber's congenital amaurosis 66%, centro-peripheral dystrophy 75%, typical retinitis pigmentosa 95%. This data shows that the poor success rate is not due to the constricted visual field but to the combined central and peripheral visual impairment. The type of aids most commonly prescribed were spectacle corrections, bifocals, hand magnifiers and the Visolett (paperweight type magnifier). The Visolett (paperweight type magnifier) has proven to be the most suitable non-spectacle magnifier used by itself, or in addition to a spectacle magnifier. Telescopic spectacles were rarely found to be of any value. The data showed that the correction of these diseases consisted of a refraction and strong reading addition in 65% of the patients.

Adolescent↗
PubMed2000

Ambient hypoxia reverses retinal vascular attenuation in a transgenic mouse model of autosomal dominant retinitis pigmentosa.

PURPOSE: Loss of retinal capillaries is an inherent component of late stage autosomal dominant retinitis pigmentosa (ADRP). This study examined the hypothetical role of tissue hyperoxia in this vascular attenuation process and tested the potential of ambient hypoxia to reverse it. METHODS: Transgenic mice expressing a mutant opsin gene with a 3-bp deletion of isoleucine at codon 255/256 were used. This model is characterized by early onset of a rapidly progressing retinal degeneration that by postnatal day (P)20 results in the loss of all but one row of photoreceptor nuclei. At P20 some mice were placed in 12% oxygen until they were euthanatized at P26. The remainder were maintained in normoxia and killed at the same age. Retinas were dissected, stained for ADPase, and flat-mounted. RESULTS: Deep plexus capillary density was significantly different in normoxic normals versus transgenics at 20 days of age (P: </= 0. 005). An additional 65% reduction of capillary density occurred within the deep plexus of normoxic transgenics between P20 and P26 (P: </= 0.005). Ambient hypoxia between days P20 and P26 reversed this trend, causing an increase in deep capillary plexus density of nearly 100% (P: </= 0.001). CONCLUSIONS: This model of ADRP demonstrates two important features of human retinitis pigmentosa: photoreceptor cell death and subsequent retinal capillary atrophy. Low ambient oxygen was used to reverse the capillary atrophy and to stimulate new capillary growth, implying that retinal oxygen tension may link these two features of the pathology. The implications of this study hold importance for strategies designed to treat retinitis pigmentosa with retinal cell transplantation.

Animals↗
PubMed1996

Abnormalities of the retinal cone system in retinitis pigmentosa.

Patients with retinitis pigmentosa (RP) show delayed inner retinal responses as measured by the cone ERG response to a 30 Hz stimulus. To determine the extent to which this delay results from abnormalities of cone phototransduction, cone ERGs to single flashes were obtained from 21 patients with RP and a model of cone phototransduction was fitted to the leading edge of the a-waves of these ERGs. Nearly all patients showed an abnormally low sensitivity of cone phototransduction consistent with a reduction in the amplification of transduction. This abnormality can account for part of the delayed 30 Hz response. Analysis of post-receptoral potentials indicated that RP also slows the responses of the inner retina. A combination of these two factors, a sensitivity change at the receptor and a delay in the response of the inner retina, produces the delayed response of the cone flicker ERG in patients with RP.

Adaptation, Ocular↗
PubMed1997

[Color Doppler ultrasonography in retinitis pigmentosa. Preliminary study].

PURPOSE: Retinitis pigmentosa is a bilateral retinal degeneration. The primary disorder is still debated. METHODS: We performed a prospective investigation of the ocular circulation directly by color Doppler imaging (CDI). A total of 28 eyes of 14 patients (8 men and 6 women, affected with retinitis pigmentosa) were recruited for this study. For each case were evaluated protosystolic velocity and the resistive index of the ophthalmic artery, central retinal artery, posterior ciliary arteries and choroid. These values, furthermore, have been compared with a control group. RESULTS: The results of the CDI in the group of RP and in the CG were: in the OA: PSV 31.177 +/- 5.119 cm/sec vs 36.700 +/- 3.152 cm/sec (p < 0.007); RI 0.713 +/- 0.058 vs 0.717 +/- 0.019 (p < 0.0839); in the CRA PSV 7.075 +/- 1.611 cm/sec vs 12.710 +/- 2.795 cm/sec (p < 0.001); RI 0.560 +/- 0.062 vs 0.550 +/- 0.051 (p < 0.234); in the PCA: PSV 8.569 +/- 3.408 cm/sec vs 14.100 +/- 2.571 cm/sec (p < 0.001) with RI 0.634 +/- 0.090 vs 0.681 +/- 0.045 (p < 0.145). In the CHO: PSV 12.312 +/- 2.327 cm/sec vs 16.170 +/- 1.846 cm/sec (p < 0.001) with RI 0.581 +/- 0.072 vs 0.638 +/- 0.050 (p < 0.065). CONCLUSION: Our results suggest that in the affected eyes there is a statistically significant reduction in blood flow in ophthalmic and ciliary arteries. These data offer new views on the retinitis cause of pigmentosa and possible therapeutics to be studied.

Adult↗