Leber遗传性视神经病变的研究进展

Leber遗传性视神经病变(Leber's hereditary optic neuropathy,LHON)是一种主要累及青壮年男性,导致视神经退行性变的母系遗传病.线粒体DNA(mitochondrial DNA,mtDNA)突变为LHON发病的主要分子基础.LHON不完全外显和男性好发的特征表明,其他因素(如mtDNA单体型、核修饰基因和/或环境因素等)在LHON发病中起着重要作用.     

Leber hereditary optic neuropathy

Leber hereditary optic neuropathy (LHON) is a mitochondrial genetic disease that preferentially causes blindness in young adult males, affecting about 1 in 25 000 of the British population. It is characterised by bilateral subacute loss of central vision owing to focal degeneration of the retinal ganglion cell layer and optic nerve. Over 95% of LHON cases are primarily the result of one of three mitochondrial DNA (mtDNA) point mutations, G3460A, G11778A, and T14484C, which all involve genes encoding complex I subunits of the respiratory chain. An intriguing feature of LHON is that only approximately 50% of males and approximately 10% of females who harbour a pathogenic mtDNA mutation actually develop the optic neuropathy. This marked incomplete penetrance and gender bias imply that additional mitochondrial and/or nuclear genetic factors must be modulating the phenotypic expression of LHON. It is also likely that environmental factors contribute to the onset of visual failure. However, these secondary precipitating factors remain poorly defined at present. In this review, we describe the natural history of this optic nerve disorder and highlight issues relating to clinical diagnosis, management, and genetic counselling. We also discuss the findings of recently published studies and the light they shed on the complex aetiology and pathophysiology of LHON.     

鼻内镜下视神经管减压治疗外伤性视神经病变

目的：探讨鼻内镜下视神经减压治疗外伤性视神经病的疗效以及影响因素。方法：回顾性分析2003年10月至2012年10月期间在我院进行住院治疗的49例(50眼)外伤性视神经病变的临床资料,所有患者均在鼻内镜下施行视神经减压术,对比手术前后患者的视力情况,并对影响患者预后的影响因素进行探究。结果：49例(50眼)中术后的总有效率为44.00%(22/50),对其相关因素进行对比分析,视力级别为光感、眼前手动、视力0.02以上有较高的优势,差异有统计学意义(P<0.05)。受伤至手术时间在3 d以及7 d以内有显著的效果,差异有统计学意义(P<0.05)。而性别、年龄、术前是否应用激素冲击治疗及术中是否进行鞘膜切开分组比较,差异无统计学意义(P>0.05)。结论：鼻内镜下视神经减压术治疗外伤性视神经病具有一定效果,在创伤发生3d内以及术前视力在光感、眼前手动、视力0.02以上患者进行手术干预,可以获得较高的临床效果。     

线粒体单倍型对Leber病的影响

在Leber遗传性视神经病变(Leber's hereditary optic neuropathy,LHON)家系中由母系传递这种视觉功能障碍,提示线粒体基因组(mitochondrial DNA,mtDNA)突变为该疾病发生的主要分子基础.在不同种族人群的LHON家系中,有50%以上是由于mtDNA编码呼吸链复合体I上ND1 G4360A,ND4 G11778A和ND6 T14484C突变引起的.这3个突变位点因为致病率高,被称为原发性突变.但是携带这些位点突变的母系成员并不是都会出现LHON症状,而且在同一个家系内或不同家系间携带相同mtDNA突变的患者在发病年龄、视力损伤程度和发病过程也都不完全一样.这提示可能这些LHON相关的原发性突变本身不足以导致临床表现.IMON的男性多发、不完全外显和不同的基因表现度表明还有其他因素在疾病的发生发展过程起到修饰作用,这些因素包括:个人因素、环境因素、核修饰基因和mtDNA单倍型.特别是mtDNA单倍型,在对携带3个LHON相关原发性突变的家系中母系成员的发病起到协同作用.     

Leber遗传性视神经病变线粒体DNA突变的研究

目的 探讨Leber遗传性视神经病变患者的线粒体DNA突变类型及特点.方法 分别应用等位基因特异性PCR（MSP-PCR）、聚合酶链反应-限制性片段长度多态性（PCR-RFLP）和聚合酶链反应-单链构象多态性（PCR-SSCP）联合DNA测序的方法,对12个家系中21位临床症状疑诊为LHON的患者及其19位无明显眼疾的母系亲属进行线粒体DNA检测.结果 40例受检者中35例发生11778位点突变,2位成员有3460位点突变,有1例发现有4258位点突变（A→G）.结论 11778是LHON患者常见的突变位点,3460突变少见,新发现的突变位点4258可能是新的继发突变或基因多态性.     

核DNA对Leber遗传性视神经病的影响

对一个同卵双生leber病家系成员mtDNA突变状况作基因分析，并比较同卵双生子及其同胞间症状差异。发现该家系母系成员mtDNA相同皆为突变纯合型，同卵双生子间症状相似，但与他们同胞间差异极大，这种差异是由核DNA不同所致，表明核DNA在该病形成过程中影响极大。     

Diagnosis and classification of autoimmune optic neuropathy

The spectrum of autoimmune optic neuropathies (ON) is extending. The phenotypic spectrum includes single isolated optic neuritis (SION), relapsing isolated optic neuritis (RION), chronic relapsing inflammatory optic neuropathy (CRION), the neuromyelitis optica (NMO) spectrum disorder, multiple sclerosis associated optic neuritis (MSON) and unclassified optic neuritis (UCON) forms. Epidemiological data suggests a slight female predominance. The ethnic heritage is relevant as Caucasian patients are more likely to suffer from MSON, whilst SION, RION, CRION and NMO are more frequent in non-Caucasian patients. Importantly, prognosis for recovery of visual function is good in MSON, but poorer in NMO and CRION which also have a high chance for recurrent episodes. Testing for serum anti-AQP4 autoantibodies is advised in all patients with severe, atypical or recurrent ON because of the high diagnostic specificity. The diagnostic specificity may be aided by testing for glial biomarkers in the CSF and prognostic accuracy by testing for biomarkers for neuroaxonal degeneration. Optical coherence tomography is a highly accurate tool to document the final outcome. The current clinical classification criteria rely on the phenotype, response to treatment and presence of anti-AQP4 autoantibodies.     

LDL-apheresis in acute anterior ischemic optic neuropathy

Acute anterior ischemic optic neuropathy (AION) is a disabling disease which impairs visual function. Standard treatment is unable to affect the outcome and the visual damage persists. We describe the case of a 64-year-old patient affected by AION, whose only known risk factor was hypercholesterolemia. After a first onset of involvement of the right eye (RE), the patient presented four weeks later with an analogous episode affecting the left eye (LE). Since standard treatment, started at involvement of the RE, had not yielded any beneficial effect, the patient underwent three sessions of LDL apheresis. The scotomatous portion of the visual field reduced even after the first session, there was further improvement after the third, and after six months the condition remained stable. Corrected vision improved from 2/10 to 6/10 after the third session. LDL cholesterol and fibrinogen decresade after the third session from 239 mg/dL to 31 mg/dL and from 289 mg/dL to 92 mg/dL, respectively. In conclusion, thanks to its effect of antagonizing hemorheologic disorders of the ocular microcirculation, LDL apheresis seems to be an efficacious treatment of AION, especially in patients suffering from hypercholesterolemia.     

Therapeutic potentials of aspirin in glaucomatous optic neuropathy

Glaucoma is a common blinding disease worldwide. Although traditionally considered as a disease of elevated intraocular pressure, it is now clear that glaucoma is primarily a distinctive optic neuropathy with many proposed pathogenic mechanisms. Impaired blood flow resulting in ischemia has been proposed to be involved in the retinal ganglion cell loss seen in glaucoma. Aspirin might improve optic nerve head perfusion by stabilizing microcirculatory flow. Evidence also indicates that apoptosis may be the final common pathway for ganglion cell death in glaucoma. Aspirin has been shown to exhibit neuroprotective properties. Prostaglandins play an important role in the regulation of intraocular pressure. Aspirin is well known to inhibit cyclooxygenase mediated prostaglandin synthesis. The NSAID-inhibition of PGs synthesis up-regulates the concentration prostaglandin receptors in retinovascular tissues. Based on the body of evidence implicating ocular blood flow disturbances, apoptotic cell death, and also the role of prostaglandins in the pathogenesis of glaucoma we hypothesize that aspirin could be potentially useful drugs in the treatment of glaucoma. Hypothetical pathophysiologic mechanisms explaining potential beneficial effects of aspirin on glaucomatous optic neuropathy include: increasing optic nerve blood flow, preventing retinal ganglion cell death through neuroprotective mechanisms, and upregulating prostaglandin receptors.     

The clinical spectrum of alpha-L-iduronidase deficiency

We present five patients with alpha-L-iduronidase deficiency who do not have the typical Hurler or Scheie phenotypes; they are compared to 28 similarly atypical cases from the literature. Phenotypic differences are pointed out and intrafamilial similarities stressed. Among the various possible explanations for this situation, the existence of genetic compounds seems acceptable for some of the cases, but others seem to be caused by different mutations. The elucidation of these alternative possibilities from recent biochemical research is discussed.     

Leber遗传性视神经病变的遗传学进展

1871年德国眼科医生Theodor Leber首次描述了一种遗传性眼病，主要表现为双眼急性或亚急性中心视力下降。多累及青年男性，随后便将此病命名为Leber遗传性视神经病变（Leber hereditary optic neuropathy，LHON）。现已证实该病为母系遗传性疾病，其主要病因是线粒体DNA（mitochondrial DNA，mtDNA）某些位点发生突变，是一种最为常见的线粒体遗传病。尽管现在对此病已进行了深入研究。但有很多方面尚需进一步讨论，例如：有关LHON突变基因位点的研究、LHON的不完全外显性、LHON的遗传种族差异性以及突变位点与临床表现和预后的关系等，本文就这几方面进行综述。     

Risk factors in nonarteritic anterior ischemic optic neuropathy

The authors have investigated risk factors associated with the occurrence of nonarteritic anterior ischemic optic neuropathy (AION) in 83 patients and 124 eyes. 12% of the patients with nonarteritic AION had diabetes mellitus, 37.3% hypertension, 14.5% atherosclerosis, while the rest (36.2%) were classified as idiopathic. The incidence of bilateral AION was slightly less than 50%. The period in which both eyes get affected is usually 1-2 months or longer. Nonarteritic AION can occur at any age, therefore it is seen in young people as well. The role of arterial hypertension and diabetes in pathogenesis of AION is still to be determined.     

High doses of cobalt induce optic and auditory neuropathy

The adverse biological effects of continuous exposure to cobalt and chromium have been well defined. In the past, this toxicity was largely an industrial issue concerning workers exposed in occupational setting. Nevertheless, recent reports have described a specific toxicity mediated by the high levels of cobalt and chromium released by metallic prostheses, particularly in patients who had received hip implants. Clinical symptoms, including blindness, deafness and peripheral neuropathy, suggest a specific neurotropism. However, little is known about the neuropathological basis of this process, and experimental evidence is still lacking. We have investigated this issue in an experimental setting using New Zealand White rabbits treated with repeated intravenous injections of cobalt and chromium, alone or in combination. No evident clinical or pathological alterations were associated after chromium administration alone, despite its high levels in blood and tissue while cobalt–chromium and cobalt-treated rabbits showed clinical signs indicative of auditory and optic system toxicity. On histopathological examination, the animals showed severe retinal and cochlear ganglion cell depletion along with optic nerve damage and loss of sensory cochlear hair cells. Interestingly, the severity of the alterations was related to dosages and time of exposure. These data confirmed our previous observation of severe auditory and optic nerve toxicity in patients exposed to an abnormal release of cobalt and chromium from damaged hip prostheses. Moreover, we have identified the major element mediating neurotoxicity to be cobalt, although the molecular mechanisms mediating this toxicity still have to be defined.     

On the many faces of Leber hereditary optic neuropathy

Leber hereditary optic neuropathy (LHON) is a maternally inherited disorder, associated with mutations in the mitochondrial DNA, which is notorious for its aspecific presentations. Two pedigrees are described with cases that are atypical for LHON with respect to sex, age of onset, interval between the eyes becoming affected, course of the disease, concomitant disorders, additional test results, final visual acuity, and/or results of mtDNA analysis. Moreover, the pedigrees themselves did not suggest maternal inheritance. We analysed the diagnostic and clinical genetic difficulties related to the atypical aspects of these pedigrees. We conclude that mtDNA analysis is justified in every case of optic nerve atrophy with no clear cause. Identification of one of the three LHON specifically associated mtDNA mutations is essential to confirm the diagnosis.