Retinal arterial changes correlate with cerebral small-vessel disease

OBJECTIVE

To examine the relation between retinal artery disease and cerebral small-vessel disease (SVD).

METHODS

In a prospective cohort of patients with symptomatic atherosclerotic disease, the authors performed retinal photographs and brain MRI. Two ophthalmologists, not aware of the MR results, independently assessed retinal arterial narrowing, crossings, sclerosis, and tortuosity according to standard scoring lists. Two observers independently assessed white matter lesions (WML) and lacunar infarcts on the MR images. Lesions were considered abnormal only when both ophthalmologists or MR raters agreed. Cerebral SVD was defined as the presence of WML or lacunar infarcts.

RESULTS

In 179 patients, retinal photographs and brain MRI were performed. Of the 108 patients with MR signs of SVD, 92% had at least one retinal vascular abnormality; of the 71 patients without SVD, 77% had retinal pathology (p < 0.01). All types of retinal vascular pathology occurred more frequently in patients with SVD, but only retinal arterial narrowing and sclerosis differed significantly. In the 109 normotensive patients, the presence of any retinal vascular change correlated with signs of SVD (p = 0.01).

CONCLUSION

Pathologic changes in the retinal arteries parallel changes in the small cerebral arteries that cause WML and lacunes, both in hypertensive and in normotensive patients.

Prevalence of symptomatic intracranial aneurysm and ischaemic stroke in pseudoxanthoma elasticum

BACKGROUND

Pseudoxanthoma elasticum (PXE) is an heritable connective tissue disorder with clinical manifestations of the ocular, dermal, and cardiovascular system. The purpose of this study was to investigate the prevalence of symptomatic intracranial aneurysms (IAs) and ischaemic stroke (IS) in PXE.

METHODS

The records of 100 patients with PXE were retrieved. All patients were contacted and data on complications were collected. The literature was reviewed regarding PXE, ISs, and IAs.

RESULTS

No patient with PXE had a symptomatic IA as presenting symptom. One patient presented with an IS. During follow-up of 94 of the 100 patients (mean follow-up 17.1 years, range 1-49 years), none presented a symptomatic IA (3,168 retrospective patient observation years and 1, 602 prospective patient observation years). Upper gastrointestinal haemorrhage during follow-up occurred in 17 patients, in 1 patient during aspirin use. One patient has IS as presenting symptom and a recurrence during follow-up, and 7 patients had IS during follow-up. All were caused by small-vessel disease. The relative risk of IS in PXE under 65 years compared with the general population was 3.6 (95% confidence interval 3.3-4.0).

CONCLUSIONS

On the basis of the currently available data, an association between symptomatic IAs and PXE is unlikely. However, the incidence of IS, due to small-vessel disease, was increased. Antiplatelet therapy in patients with PXE may lead to a high incidence of upper gastrointestinal haemorrhages.

The 2588G-->C mutation in the ABCR gene is a mild frequent founder mutation in the Western European population and allows the classification of ABCR mutations in patients with Stargardt disease

In 40 western European patients with Stargardt disease (STGD), we found 19 novel mutations in the retina-specific ATP-binding cassette transporter (ABCR) gene, illustrating STGD's high allelic heterogeneity. One mutation, 2588G-->C, identified in 15 (37.5%) patients, shows linkage disequilibrium with a rare polymorphism (2828G-->A) in exon 19, suggesting a founder effect. The guanine at position 2588 is part of the 3' splice site of exon 17. Analysis of the lymphoblastoid cell mRNA of two STGD patients with the 2588G-->C mutation shows that the resulting mutant ABCR proteins either lack Gly863 or contain the missense mutation Gly863Ala. We hypothesize that the 2588G-->C alteration is a mild mutation that causes STGD only in combination with a severe ABCR mutation. This is supported in that the accompanying ABCR mutations in at least five of eight STGD patients are null (severe) and that a combination of two mild mutations has not been observed among 68 STGD patients. The 2588G-->C mutation is present in 1 of every 35 western Europeans, a rate higher than that of the most frequent severe autosomal recessive mutation, the cystic fibrosis conductance regulator gene mutation DeltaPhe508. Given an STGD incidence of 1/10,000, homozygosity for the 2588G-->C mutation or compound heterozygosity for this and other mild ABCR mutations probably does not result in an STGD phenotype.

Autosomal recessive retinitis pigmentosa and cone-rod dystrophy caused by splice site mutations in the Stargardt's disease gene ABCR

Ophthalmological and molecular genetic studies were performed in a consanguineous family with individuals showing either retinitis pigmentosa (RP) or cone-rod dystrophy (CRD). Assuming pseudodominant (recessive) inheritance of allelic defects, linkage analysis positioned the causal gene at 1p21-p13 (lod score 4.22), a genomic segment known to harbor the ABCR gene involved in Stargardt's disease (STGD) and age-related macular degeneration (AMD). We completed the exon-intron structure of the ABCR gene and detected a severe homozygous 5[prime] splice site mutation, IVS30+1G->T, in the four RP patients. The five CRD patients in this family are compound heterozygotes for the IVS30+1G->T mutation and a 5[prime] splice site mutation in intron 40 (IVS40+5G->A). Both splice site mutations were found heterozygously in two unrelated STGD patients, but not in 100 control individuals. In these patients the second mutation was either a missense mutation or unknown. Since thus far no STGD patients have been reported to carry two ABCR null alleles and taking into account that the RP phenotype is more severe than the STGD phenotype, we hypothesize that the intron 30 splice site mutation represents a true null allele. Since the intron 30 mutation is found heterozygously in the CRD patients, the IVS40+5G->A mutation probably renders the exon 40 5[prime] splice site partially functional. These results show that mutations in the ABCR gene not only result in STGD and AMD, but can also cause autosomal recessive RP and CRD. Since the heterozygote frequency for ABCR mutations is estimated at 0.02, mutations in ABCR might be an important cause of autosomal recessive and sporadic forms of RP and CRD.

Exclusion of PPEF as the gene causing X-linked juvenile retinoschisis

X-linked juvenile retinoschisis (RS) is a progressive vitreoretinal degeneration localised in Xp22.1-p22.2. A human homologue of the retinal degeneration gene C (rdgC), a gene that in Drosophila melanogaster prevents light-induced retinal degeneration, was localised in the RS obligate gene region. We have tested the gene, designated PPEF in humans, as a candidate gene in RS patients using RT-PCR and the protein truncation test on RNA and SSCP on DNA. No mutations were identified, making it highly unlikely that PPEF is the gene implicated in RS. The data presented facilitate mutation analysis of the PPEF gene in other diseases which have been or will be localised to this region.

A locus for autosomal recessive pseudoxanthoma elasticum, with penetrance of vascular symptoms in carriers, maps to chromosome 16p13.1

Pseudoxanthoma elasticum (PXE) is a heritable systemic disorder characterized by calcification of the elastic fibers of the connective tissue. Symptoms are predominantly noted in the eye, the skin, and the cardiovascular system, resulting in visual loss, skin lesions, and life-threatening vascular disease. In the study we combined homozygosity mapping and genome scanning with 374 markers in affected individuals from a PXE family from a genetically isolated population in The Netherlands. Initial homozygosity in two or three patients was found with up to 20 markers, among which D16S292 located in 16p13.1. Upon refined and more extensive family screening of the latter region, close linkage without recombination was found with the marker D16S764 (Zmax = 6.27). Despite clear autosomal recessive inheritance of the ocular symptoms in PXE, vascular symptoms appear in 40%-50% of the heterozygotes.

Conclusive evidence for a distinct congenital stationary night blindness locus in Xp21.1

X linked congenital stationary night blindness (CSNBX) is a non-progressive retinal disorder characterised by decreased visual acuity and disturbance of night vision. CSNBX appears to be not only clinically but also genetically heterogeneous. On studying a single large family, we recently suggested the presence of a distinct locus for CSNBX in Xp21.1. Here, we describe the results of a linkage analysis in another large CSNBX family, which confirms this finding. Thus, the data presented here provide conclusive evidence for a distinct CSNBX locus in Xp21.1, closely linked to the X linked retinitis pigmentosa type 3 gene. The results combined with other published results indicate the order Xpter-DXS451-DMD-DYS1-(DXS1110, CSNBX1, XLRP3)-DXS7-(CSNBX2, XLRP2)-DXS14-Xcen.

Localization of a novel X-linked congenital stationary night blindness locus: close linkage to the RP3 type retinitis pigmentosa gene region

X-linked congenital stationary night blindness (CSNBX) is a non-progressive retinal disorder characterized by decreased visual acuity and loss of night vision. CSNBX is clinically heterogeneous with respect to the involvement of retinal rods and/or cones in the disease. In this study, we localize a new locus for CSNBX to Xp21.1, thus providing evidence that CSNBX is also genetically heterogeneous. A clear correlation between different genotypes and phenotypes cannot be found yet. The new CSNBX gene described here is closely linked to the X-linked retinitis pigmentosa type 3 gene region, which supports the hypothesis that there may be a functional relationship between congenital stationary night blindness and retinitis pigmentosa.