Pseudoxanthoma elasticum

Pseudoxanthoma elasticum (PXE) is an inherited disorder that is associated with accumulation of mineralized and fragmented elastic fibers in the skin, vessel walls, and Bruch's membrane. Clinically, patients exhibit characteristic lesions of the skin (soft, ivory-colored papules in a reticular pattern that predominantly affect the neck), the posterior segment of the eye (peau d'orange, angioid streaks, choroidal neovascularizations), and the cardiovascular system (peripheral arterial occlusive disease, coronary occlusion, gastrointestinal bleeding). There is no causal therapy. Recent studies suggest that PXE is inherited almost exclusively as an autosomal recessive trait. Its prevalence has been estimated to be 1:25,000-100,000. The ABCC6 gene on chromosome 16p13.1 is associated with the disease. Mutations within the ABCC6 gene cause reduced or absent transmembraneous transport that leads to accumulation of substrate and calcification of elastic fibers. Although based on clinical features the diagnosis appears readily possible, variability in phenotypic expressions and the low prevalence may be responsible that the disease is underdiagnosed. This review covers current knowledge of PXE and presents therapeutic approaches.     

Pseudoxanthoma Elasticum: Genetics, Clinical Manifestations and Therapeutic Approaches

Pseudoxanthoma elasticum (PXE) is an inherited disorder that is associated with accumulation of mineralized and fragmented elastic fibers in the skin, vascular walls, and Bruch's membrane in the eye. Clinically, patients exhibit characteristic lesions of the posterior segment of the eye including peau d'orange, angioid streaks, and choroidal neovascularisations, of the skin including soft, ivory-colored papules in a reticular pattern that predominantly affect the neck and large flexor surfaces, and of the cardiovascular system with peripheral and coronary arterial occlusive disease as well as gastrointestinal bleedings. There is yet no definitive therapy. Recent studies suggest that PXE is inherited almost exclusively as an autosomal recessive trait. Its prevalence has been estimated to be 1:25,000-100,000. Very recently, the ABCC6 gene on chromosome 16p13.1 was found to be associated with the disease. Mutations within ABCC6 cause reduced or absent transmembraneous transport that leads to accumulation of extracellular material. Presumably, this mechanism causes calcification of elastic fibers. Despite the characteristic clinical features, the variability in phenotypic expressions, and the low prevalence may be responsible for the disease being underdiagnosed. This review compiles and summarizes current knowledge of PXE pathogenesis and clinical findings. Furthermore, different therapeutic strategies to treat retinal manifestations are discussed, including thermal laser coagulation, photodynamic therapy, and intravitreal injections of drugs inhibiting vascular endothelial growth factor.     

Novel mutation in ABCC6 gene in a Japanese pedigree with pseudoxanthoma elasticum and retinitis pigmentosa

PURPOSE: To report a novel mutation of the ABCC6 gene in a Japanese family that had a case of pseudoxanthoma elasticum (PXE) another with PXE and retinitis pigmentosa. METHODS: Ophthalmologic examinations were performed, and the ABCC6 gene was analysed by direct genomic sequencing. RESULTS: Fundus examinations of the 48-year-old proband disclosed angioid streaks and a peud'orange appearance of the retina of the both eyes, whereas both of his 25- and 20-year-old daughters had pigmentary degeneration and angioid streaks. In the sibilings, the mixed cone-rod ERG was almost nondetectable, whereas that of the proband was well-preserved. Molecular genetic analysis revealed that the proband has a homozygous nonsense mutation at the 595 bp in the ABCC6, and the siblings were heterozygous for the same mutation. This mutation was not detected in Japanese subjects in the JSNP database (http://snp.ims.u-tokyo.ac.jp/). CONCLUSIONS: Our results demonstrated an association between a novel mutation in the ABCC6 gene and PXE in a Japanese family.     

Ocular findings in four siblings with pseudoxanthoma elasticum

In a family consisting of 8 surviving siblings, pseudoxanthoma elasticum was diagnosed in 4 sisters. One of them had a severe visual handicap, and another a slight decrease of the visual acuity because of the ocular lesions. The other 2 sisters also had fundal lesions, but they were visually symptom-free. Great variation was also found in the appearance of the ocular lesions in the affected siblings. In addition to the angioid streaks, the fundal findings in the probands affected included changes of the retinal pigment epithelium, exudative maculopathy, optic disc drusen and 'fire-work'-pattern of drusen of the Bruch's membrane. A similar variety of alterations was also found in the histopathology of the skin.     

The pathogenesis of the fundus peau d'orange and salmon spots

The fundus of the eye of a patient with pseudoxanthoma elasticum showed angioid streaks, fundus peau d'orange and salmon spots, these latter unusually located in the macula. The fluorescein angiography revealed, in the arterial phase, a reticular hyperfluorescence in the areas of fundus peau d'orange and salmon spots. In the venous phase the fluorescence of the fundus peau d'orange was even, while the salmon spots showed staining and hyperfluorescent borders. These findings support the hypothesis that the fundus peau d'orange is due to degeneration of Bruch's membrane and the salmon spots are deiscences of this membrane.     

Diagnosis and management of angioid streaks

Angioid streaks are asymptomatic breaks in Bruch's membrane developing later in life. Secondary macular degeneration and other fundus abnormalities often accompany their development. Angioid streaks are frequently associated with systemic diseases such as pseudoxanthoma elasticum, Paget's disease of bone, and the sickle cell hemoglobinopathies. The clinical manifestations of angioid streaks, related fundus changes, and these three systemic disorders are discussed as well as principles of treatment and management. Two case reports are presented which illustrate some of the important characteristics of angioid streaks.     

Optic disc drusen, angioid streaks, and mottled fundus in various combinations in a Sicilian family

BACKGROUND: We describe a Sicilian family in which optic disc drusen, angioid streaks, and mottled fundus--without dermatological signs of pseudoxanthoma elasticum (PXE)--are present in various combinations and segregate as an autosomal dominant trait. Since these ocular manifestations can be part of the clinical signs of PXE, we examined the possible involvement of a mutation in the ABCC6 gene, which is known to be responsible for PXE. METHODS: Linkage analysis was performed with both intragenic and flanking markers. We used marker D16B9722 and a single-nucleotide polymorphism located in exon 15 of the ABCC6 gene. LOD score values were calculated on the assumption of a gene frequency of 0.0001 and both complete penetrance and reduced penetrance (90%), with theta values between 0.0 and 0.4. RESULTS: LOD score values excluded the involvement of the ABCC6 gene. CONCLUSIONS: The dominant transmission of optic disc drusen, mottled fundus, and angioid streaks in this family is not due to alterations in the ABCC6 gene.     

Analysis of the frequent R1141X mutation in the ABCC6 gene in pseudoxanthoma elasticum

PURPOSE: To characterize the ABCC6 R1141X nonsense mutation, which is implicated in more than 25% of a cohort of patients from The Netherlands with pseudoxanthoma elasticum (PXE). METHODS: A combination of single-strand conformational polymorphism (SSCP), PCR, sequencing, and Southern blot analysis was used to identify mutations in the ABCC6 gene in 62 patients. Haplotypes of 16 patients with the R1141X mutation were determined with eight polymorphic markers spanning the ABCC6 locus. The effect of the R1141X mutation on the expression of ABCC6 was studied in leukocytes and cultured dermal fibroblasts from affected skin in patients heterozygous or homozygous for the R1141X mutation. ABCC6 expression was analyzed by RT-PCR and immunocytochemistry with ABCC6-specific monoclonal antibodies. RESULTS: The ABCC6 R1141X mutation was found on 19 alleles in 16 patients with PXE and occurred in heterozygous, homozygous, or compound heterozygous form. All R1141X alleles were associated with a common haplotype, covering at least three intragenic ABCC6 markers. None of the patients or healthy control subjects had a similar ABCC6 haplotype. Furthermore, the results showed that the expression of the normal allele in R1141X heterozygotes was predominant, whereas no detectable, or very low, ABCC6 mRNA levels were found in R1141X homozygotes. Immunocytochemical staining of cultured dermal fibroblasts with ABCC6-specific monoclonal antibodies showed no evidence of the presence of a truncated protein in patients with PXE who were homozygous for R1141X. CONCLUSIONS: A specific founder effect for the R1141X mutation exists in Dutch patients with PXE. The R1141X mutation induces instability of the aberrant mRNA. Functional haploinsufficiency or loss of function of ABCC6 caused by mechanisms, such as nonsense-mediated decay (NMD), may be involved in the PXE phenotype.     

Atypical drusen in pseudoxanthoma elasticum.

Forty-three patients with pseudoxanthoma elasticum were evaluated ophthalmologically. The fundus appearance was characterized by angioid streaks and mottling of the retinal pigment epithelium. Rock-like atypical drusen were present in the posterior pole or peripheral retina in 75% of the patients examined and were an integral part of this fundus picture. These drusen changed little with time and were seen in early stages of pseudoxanthoma elasticum. The histopathology of these drusen is unknown.     

Bruch's membrane in pseudoxanthoma elasticum

Summary In a case of pseudoxanthoma elasticum (PXE), Bruch's membrane was studied histochemically, ultrastructurally and by element analysis. Two kinds of calcifications were observed, one composed of hydroxyapatite and the other of CaHPO₄. They were seen in the scar tissue of angioid streak areas and in the membrane outside these areas, respectively. Furthermore, a thready material was found in the membrane as well as an increased amount of acid mucopolysaccharides. The genesis of the calcifications and the pathogenesis of angioid streaks are discussed. The author is in favor of a malformed collagen as the basic defect in PXE.This paper was presented at the Fifth Annual Meeting of the European Club for Ophthalmic Fine Structure in Zurich, Switzerland, on March 25 and 26, 1977The work was supported by a grant from Statens Lægevigenskabelige Forskningsråd     

Society tidings

Purpose: To emphasize the importance of the association of optic disc drusen (ODD) with angioid streaks (AS). Methods: Three patients with ODD and AS underwent a thorough ophthalmic examination including perimetry and B-scan ultrasonography. Fundus fluorescein angiography was performed when indicated. Results: Bilateral ODD associated with AS were present in all of the cases. Pseudoxanthoma elasticum was the definite etiology of the AS in two cases, one of which was complicated by subretinal neovascularization. Laser photocoagulation resulted in closure of the membrane. Conclusions: The follow-up of patients with ODD with regard to the development of AS is essential as ODD may be the earliest clinical manifestation in patients with pseudoxanthoma elasticum, which has potential vision- and life-threatening complications.     

Pseudoxanthoma elasticum,ocular manifestations,complications and treatment

Pseudoxanthoma elasticum (PXE), also known as Groenblad syndrome, is an inherited disorder characterised by mineralisation and fragmentation of elastic fibres in a number of organs including the skin, eyes and arterial blood vessels. The clinical manifestations of PXE centre on three major organ systems: skin, cardiovascular system and the eyes. This review focuses on the ocular manifestations of pseudoxanthoma elasticum, namely, peau d'orange, angioid streaks and choroidal neovascularisation, the clinical course of patients, the diagnostic approaches and current therapeutic strategies, such as laser photocoagulation whether transpupillary thermotherapy or photodynamic therapy, macular translocation surgery and anti‐vascular endothelial growth factor treatment.     

The etiology of choroidal folds

Folding of the choroid, Bruch's membrane, and the overlying retina occurs in a variety of ocular and orbital diseases and after certain surgical procedures. The etiology of the folding is explained, using the principles of deformation of materials and by considering the biomechanical properties of the choroid and sclera. Choroidal folds are likely to develop in association with any intra- or extraocular process that induces sufficient compressive stress within the choroid, Bruch's membrane, and retina to force these tissues to buckle. A detailed explanation of the pathogenesis of folding is presented in various clinical settings.     

Macular translocation for subfoveal choroidal neovascularization in angioid streaks

PURPOSE: To report a case of visual improvement after macular translocation performed for a subfoveal choroidal neovascular membrane in a patient with pseudoxanthoma elasticum and angioid streaks. METHODS: The fovea was translocated inferiorly by scleral imbrication, intentional retinal detachment with a small posterior retinotomy, and partial fluid-air exchange. The choroidal neovascular membrane was photocoagulated 1 week later. RESULTS: The visual acuity of the patient improved from 20/125 to 20/40. The center of the foveal avascular zone was moved inferiorly 844 microm. The choroidal neovascular membrane was extrafoveal after translocation and was treated with laser photocoagulation. CONCLUSION: Macular translocation may be considered in the management of subfoveal choroidal neovascular membrane in patients with pseudoxanthoma elasticum and angioid streaks.     

Disk drusen and angioid streaks in pseudoxanthoma elasticum

Visual field loss secondary to optic disk drusen became evident before the development of angioid streaks in a patient with pseudoxanthoma elasticum. The incidence of optic disk drusen in cases of pseudoxanthoma elasticum is 20 to 50 times greater than that in the healthy population. We postulate that the abnormal aggregation of macromolecules with a high affinity for calcium (resulting in abnormalities in elastin in cases of pseudoxanthoma elasticum) also develops at the cribriform plate, disrupting axonal flow and leading to disk drusen formation. Pseudoxanthoma elasticum is associated with marked cardiovascular and gastrointestinal morbidity. Moreover, macular hemorrhage and precipitation of angioid streaks have frequently been noted after trauma. Prompt diagnosis of pseudoxanthoma elasticum will allow necessary prophylaxis and must be considered in patients with optic disk drusen.     

Tomographic fundus features in pseudoxanthoma elasticum: comparison with neovascular age-related macular degeneration in Japanese patients

PurposeTo determine the retinal and subretinal features characteristic to pseudoxanthoma elasticum (PXE) compared with age-related macular degeneration by using spectral-domain optical coherence tomography (SD-OCT) in Japanese patients.MethodsWe reviewed colour fundus photographs, fluorescein angiograms, and SD-OCT images of 52 eyes (27 Japanese patients) with angioid streaks (AS) due to PXE. Then we compared the incidence of tomographic features between 24 eyes (24 patient) with choroidal neovascularization (CNV) secondary to AS and 44 eyes (44 patients) with CNV secondary to age-related macular degeneration (AMD).ResultsSecondary CNV was found in 44 eyes (84.6%) of 52 patients with PXE during follow-up. We found characteristic round or ovoid tubular structures with highly reflective annular lines (termed 'outer retinal tubulation' (ORT)) in 31 (70.5%) of 44 eyes with CNV, but none were found in eyes without CNV. We also found characteristic undulations of Bruch's membrane in 38 (73.1%) eyes with AS. The incidence of ORT was significantly greater in eyes with CNV secondary to AS (70.8%; P=0.005) compared with eyes with CNV secondary to AMD (34.1%). The incidence of Bruch's membrane undulation was significantly greater in eyes with CNV secondary to AS (70.8%; P<0.0001) than in eyes with CNV secondary to AMD (11.4%).ConclusionSD-OCT imaging clearly revealed a greater incidence of unique lesions, including ORT and Bruch's membrane undulation, in eyes in PXE patients with CNV secondary to AS than in eyes with CNV secondary to AMD.     

Periocular injection of microspheres containing PKC412 inhibits choroidal neovascularization in a porcine model

PURPOSE: Oral administration of PKC412, a kinase inhibitor that blocks several isoforms of protein kinase C (PKC) and receptors for vascular endothelial growth factor (VEGF), platelet-derived growth factor, and stem cell factor, inhibits ocular neovascularization in a murine model. The purpose of this study was to determine whether sustained local delivery of PKC412 in a human-sized eye inhibits choroidal neovascularization (CNV). METHODS: Laser photocoagulation was used to rupture Bruch's membrane in young domestic pigs, and then a periocular injection of control microspheres or microspheres containing 25% or 50% PKC412 was given. After 10 days the integrated area of CNV at Bruch's membrane rupture sites was measured by image analysis. The levels of PKC412 in choroid, retina, and vitreous were measured either 10 or 20 days after periocular injection of 50% PKC microspheres or at 20 days after injection of 25% PKC412 microspheres. RESULTS: The areas of CNV at Bruch's membrane rupture sites were significantly smaller in eyes that received a periocular injection of microspheres containing 25% (P=0.0042) or 50% (P=0.0012) PKC412 than those in eyes injected with control microspheres. Ten days after periocular injection of 50% PKC412 microspheres, PKC412 was detected in the choroid, but not in the retina or vitreous. Twenty days after periocular injection of 50% PKC412, high levels of PKC412 were measured in the choroid, vitreous, and retina. Levels were lower but still substantial in all three compartments 20 days after periocular injection of 25% microspheres. CONCLUSIONS: Sustained local delivery of PKC412 provides a promising approach for treatment of CNV.     

Membrana neovascular subretiniana asociada a estrías angioides tratada con bevacizumab intravítreo

IntroductionAngioid streaks are breaks in Bruch's membrane that may be associated, among others, with pseudoxanthoma elasticum. Its most common complication is the development of subretinal neovascular membranes (SRNVM) and the decreased vision this entails.Case reportA 28 year old woman with angioid streaks and SRNVM in the left eye, who received 3 injections of intravitreal bevacizumab, with rapid improvement in vision and stability during 11 months follow up. The finding of angioid streaks led to the diagnosis of pseudoxanthoma elasticum.ConclusionIntravitreal bevacizumab should be considered as an effective treatment option for choroidal neovascularization associated with angioid streaks.     

视网膜色素上皮、Bruch膜及脉络膜的老年性黄斑变性改变

目的研究并定量分析视网膜色素上皮(retinalpigment epithelium,RPE)、Bruch膜和脉络膜的老年性改变及在老年黄斑变性眼的改变。方法应用改良Masson三色组织染色法及电脑图像分析软件,对36例不同龄正常眼及6例老年黄斑变性(age—related macular degenera—tion,ARMD)眼的RPE数量和形态、Bruch膜的厚度和脉络膜毛细血管的密度及脉络膜厚度进行定量分析研究及讨论。结果RPE老年性形态改变包括数量的减少及细胞高度的增加伴有Bruch膜增厚(老年性黄斑变性);但脉络膜毛细血管密度及脉络膜的厚度与年龄未见明显的关系。ARMD眼主要表现为RPE形态明显改变及基底膜线样沉着物形成,Bruch膜增厚。结论RPE以及Bruch膜的改变可能是早期和基础性的老年性改变,其进一步的变化可能导致脉络膜及视网膜的损害。     

Morphologic fluorescein angiographic, and light microscopic features of experimental choroidal neovascularization

We induced choroidal neovascularization in the rhesus monkey by impoverishing the blood supply to the inner retina and producing defects in Bruch's membrane by photocoagulation. Fourteen of 46 eyes undergoing photocoagulation developed neovascular fronds which were identified and categorized by histopathologic examination and fluorescein angiography. All new vessels gained access to the retina through defects in Bruch's membrane at the site of photocoagulation marks. In eight eyes the new vessels remained localized to the immediate vicinity of photocoagulation marks. In four eyes neovascular fronds infiltrated the subretinal space for distances up to 6 disk diameters from the point of entry into the retina. In the two eyes choroidovitreal neovascular complexes developed but rapidly regressed shortly after gaining the vitreous cavity. Fluorescein angiography demonstrated that all neovascular fronds were grossly incompetent to dye but that formed feeding channels had some degree of integrity. Light microscopic studies showed the proliferating networks to be composed of capillaries with well-formed basement membranes and more mature vessels with the basic structure of choroidal arteries and veins.