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Leber's hereditary optic neuropathy (LHON) is a mitochondrially inherited (transmitted from mother to offspring) degeneration of
retinal ganglion cell A retinal ganglion cell (RGC) is a type of neuron located near the inner surface (the ganglion cell layer) of the retina of the eye. It receives visual information from photoreceptors via two intermediate neuron types: bipolar cells and reti ...
s (RGCs) and their
axon An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action p ...
s that leads to an acute or subacute loss of central vision; it predominantly affects young adult males. LHON is transmitted only through the mother, as it is primarily due to
mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, m ...
s in the mitochondrial (not nuclear)
genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ...
, and only the egg contributes
mitochondria A mitochondrion (; ) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...
to the
embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
. LHON is usually due to one of three pathogenic mitochondrial DNA (mtDNA)
point mutation A point mutation is a genetic mutation where a single nucleotide base is changed, inserted or deleted from a DNA or RNA sequence of an organism's genome. Point mutations have a variety of effects on the downstream protein product—consequence ...
s. These mutations are at
nucleotide Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecu ...
positions 11778 G to A, 3460 G to A and 14484 T to C, respectively in the ND4, ND1 and ND6 subunit
gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
s of complex I of the
oxidative phosphorylation Oxidative phosphorylation (UK , US ) or electron transport-linked phosphorylation or terminal oxidation is the metabolic pathway in which cells use enzymes to oxidize nutrients, thereby releasing chemical energy in order to produce adenosine t ...
chain in mitochondria. Men cannot pass on the disease to their offspring.


Signs and symptoms

Clinically, there is an acute onset of visual loss, first in one eye, and then a few weeks to months later in the other. Onset is usually young adulthood, but age range at onset from 7-75 is reported. The age of onset is slightly higher in females (range 19–55 years: mean 31.3 years) than males (range 15–53 years: mean 24.3). The male-to-female ratio varies between mutations: 3:1 for 3460 G>A, 6:1 for 11778 G>A and 8:1 for 14484 T>C. This typically evolves to very severe optic atrophy and a permanent decrease of
visual acuity Visual acuity (VA) commonly refers to the clarity of vision, but technically rates an examinee's ability to recognize small details with precision. Visual acuity is dependent on optical and neural factors, i.e. (1) the sharpness of the retinal ...
. Both eyes become affected either simultaneously (25% of cases) or sequentially (75% of cases) with a median inter-eye delay of 8 weeks. Rarely, only one eye is affected. In the acute stage, lasting a few weeks, the affected eye demonstrates an oedematous appearance of the nerve fiber layer, especially in the arcuate bundles and enlarged or telangiectatic and tortuous peripapillary vessels (microangiopathy). The main features are seen on fundus examination, just before or after the onset of visual loss. A pupillary defect may be visible in the acute stage as well. Examination reveals decreased visual acuity, loss of
color vision Color vision, a feature of visual perception, is an ability to perceive differences between light composed of different wavelengths (i.e., different spectral power distributions) independently of light intensity. Color perception is a part of ...
and a cecocentral
scotoma A scotoma is an area of partial alteration in the field of vision consisting of a partially diminished or entirely degenerated visual acuity that is surrounded by a field of normal – or relatively well-preserved – vision. Every normal mam ...
on visual field examination.


LHON with demyelinating lesions or LHON Plus

LHON Plus is a rare variant of the disorder with eye disease together with other conditions. Its symptoms include loss of the brain's ability to control the movement of muscles, tremors, and
cardiac arrhythmia Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adult ...
. Many cases of LHON plus have been compared to
multiple sclerosis Multiple (cerebral) sclerosis (MS), also known as encephalomyelitis disseminata or disseminated sclerosis, is the most common demyelinating disease, in which the insulating covers of nerve cells in the brain and spinal cord are damaged. This ...
because of the lack of muscular control and the presence of demyelinating lesions in the CNS. It is therefore a subtype of MS, according to McDonald's definition.


Genetics

Leber hereditary optic neuropathy is a condition related to changes in
mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...
. Although most DNA is packaged in chromosomes within the nucleus, mitochondria have a distinct mitochondrial genome composed of mtDNA. Mutations in the MT-ND1,
MT-ND4 MT-ND4 is a gene of the mitochondrial genome coding for the NADH-ubiquinone oxidoreductase chain 4 (ND4) protein. The ND4 protein is a subunit of NADH dehydrogenase (ubiquinone), which is located in the mitochondrial inner membrane and is t ...
, MT-ND4L, and
MT-ND6 MT-ND6 is a gene of the mitochondrial genome coding for the NADH-ubiquinone oxidoreductase chain 6 protein (ND6). The ND6 protein is a subunit of NADH dehydrogenase (ubiquinone), which is located in the mitochondrial inner membrane and is the ...
genes cause Leber hereditary optic neuropathy. These genes code for the
NADH dehydrogenase NADH dehydrogenase is an enzyme that converts nicotinamide adenine dinucleotide (NAD) from its reduced form (NADH) to its oxidized form (NAD+). Members of the NADH dehydrogenase family and analogues are commonly systematically named using the for ...
protein involved in the normal mitochondrial function of
oxidative phosphorylation Oxidative phosphorylation (UK , US ) or electron transport-linked phosphorylation or terminal oxidation is the metabolic pathway in which cells use enzymes to oxidize nutrients, thereby releasing chemical energy in order to produce adenosine t ...
. Oxidative phosphorylation uses a series of four large multienzyme complexes, all embedded in the inner mitochondrial membrane, to convert oxygen and simple sugars to energy. Mutations in any of the genes disrupt this process to cause a variety of syndromes depending on the type of mutation and other factors. It remains unclear how these genetic changes cause the death of cells in the optic nerve and lead to the specific features of Leber hereditary optic neuropathy.


Pathophysiology

The eye pathology is limited to the retinal ganglion cell layer, especially the maculopapillary bundle. Degeneration is evident from the retinal ganglion cell bodies to the axonal pathways leading to the lateral geniculate nuclei. Experimental evidence reveals impaired glutamate transport and increased
reactive oxygen species In chemistry, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (). Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen. The reduction of molecular oxygen () p ...
(ROS) causing
apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes ( morphology) and death. These changes in ...
of retinal ganglion cells. Also, experiments suggest that normal, non-LHON-affected retinal ganglion cells produce less of the potent
superoxide In chemistry, a superoxide is a compound that contains the superoxide ion, which has the chemical formula . The systematic name of the anion is dioxide(1−). The reactive oxygen ion superoxide is particularly important as the product of t ...
radical Radical may refer to: Politics and ideology Politics * Radical politics, the political intent of fundamental societal change *Radicalism (historical), the Radical Movement that began in late 18th century Britain and spread to continental Europe an ...
than other normal central nervous system neurons. Viral vector experiments that augment
superoxide dismutase Superoxide dismutase (SOD, ) is an enzyme that alternately catalyzes the dismutation (or partitioning) of the superoxide () radical into ordinary molecular oxygen (O2) and hydrogen peroxide (). Superoxide is produced as a by-product of oxygen ...
2 in LHON cybrids or LHON animal models or use of exogenous
glutathione Glutathione (GSH, ) is an antioxidant in plants, animals, fungi, and some bacteria and archaea. Glutathione is capable of preventing damage to important cellular components caused by sources such as reactive oxygen species, free radicals, pe ...
in LHON cybrids have been shown to rescue LHON-affected retinal ganglion cells from apoptotic death. These experiments may in part explain the death of LHON-affected retinal ganglion cells in preference to other central nervous system neurons that also carry LHON-affected mitochondria.


Diagnosis

Without a known family history of LHON the diagnosis usually requires a neuro-ophthalmological evaluation and blood testing for mitochondrial DNA assessment. It is important to exclude other possible causes of vision loss and associated syndromes such as heart electrical conduction system abnormalities.


Treatment

The prognosis for those left untreated is almost always continued significant visual loss in both eyes. Regular corrected
visual acuity Visual acuity (VA) commonly refers to the clarity of vision, but technically rates an examinee's ability to recognize small details with precision. Visual acuity is dependent on optical and neural factors, i.e. (1) the sharpness of the retinal ...
and perimetry checks are advised for affected people. There is beneficial treatment for some cases of LHON, especially for early-onset disease, and experimental treatment protocols are in progress.
Genetic counseling Genetic counseling is the process of investigating individuals and families affected by or at risk of genetic disorders to help them understand and adapt to the medical, psychological and familial implications of genetic contributions to disease; t ...
should be offered. Health and lifestyle choices should be reassessed, particularly in light of toxic and nutritional theories of gene expression. Vision aids assistance and work rehabilitation should be used to assist in maintaining employment. For those who carry a LHON mutation, preclinical markers may be used to monitor progress. For example, fundus photography can monitor
nerve fiber layer The retinal nerve fiber layer (RNFL) or nerve fiber layer, stratum opticum, is formed by the expansion of the fibers of the optic nerve; it is thickest near the optic disc, gradually diminishing toward the ora serrata. As the nerve fibers pass th ...
swelling.
Optical coherence tomography Optical coherence tomography (OCT) is an imaging technique that uses low-coherence light to capture micrometer-resolution, two- and three-dimensional images from within optical scattering media (e.g., biological tissue). It is used for medica ...
can be used for more detailed study of retinal nerve fiber layer thickness. Red green
color vision Color vision, a feature of visual perception, is an ability to perceive differences between light composed of different wavelengths (i.e., different spectral power distributions) independently of light intensity. Color perception is a part of ...
testing may detect losses.
Contrast sensitivity Contrast is the contradiction in luminance or colour that makes an object (or its representation in an image or display) distinguishable. In visual perception of the real world, contrast is determined by the difference in the colour and bright ...
may be diminished. There could be an abnormal electroretinogram or visual evoked potentials. Neuron-specific enolase and axonal heavy chain
neurofilament Neurofilaments (NF) are classed as type IV intermediate filaments found in the cytoplasm of neurons. They are protein polymers measuring 10 nm in diameter and many micrometers in length. Together with microtubules (~25 nm) and mi ...
blood markers may predict conversion to affected status. Cyanocobalamin (a form of B12) should be avoided as it may lead to blindness in LHON patients. Avoiding optic nerve toxins is generally advised, especially tobacco and alcohol. Certain prescription drugs are potential risks, so all drugs should be treated with suspicion and checked before use by those at risk. Ethambutol, in particular, has been implicated as triggering visual loss in carriers of LHON. In fact, toxic and nutritional optic neuropathies may have overlaps with LHON in symptoms, mitochondrial mechanisms of disease and management. And when a patient with LHON or toxic/nutritional optic neuropathy has a
hypertensive crisis Severely elevated blood pressure (equal to or greater than a systolic 180 or diastolic of 120—sometimes termed malignant or accelerated hypertension) is referred to as a hypertensive crisis, as blood pressure at this level confers a high risk ...
as a possible complication of the disease process,
nitroprusside Sodium nitroprusside (SNP), sold under the brand name Nitropress among others, is a medication used to lower blood pressure. This may be done if the blood pressure is very high and resulting in symptoms, in certain types of heart failure, and ...
(trade name: Nipride) should not be used, due to increased risk of optic nerve ischemia in response to this anti-hypertensive. IdebenoneClinical Idebenone trial recruiting at Newcastle University U
http://lhon.ncl.ac.uk
/ref> has been shown in a small placebo-controlled trial to have modest benefit in about half of patients. People most likely to respond best were those treated early in onset. α-
Tocotrienol The vitamin E family comprise four tocotrienols (alpha, beta, gamma, delta) and four tocopherols (alpha, beta, gamma, delta). The critical chemical structural difference between tocotrienols and tocopherols is that tocotrienols have unsaturated ...
-quinone, a
vitamin E Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols. Vitamin E deficiency, which is rare and usually due to an underlying problem with digesting dietary fat rather than from a diet low in vi ...
metabolite, has had some success in small open-label trials in reversing early onset vision loss.Sadun, A et al. "EPI-743 alters the natural history of progression of Leber hereditary optic neuropathy". AOS meeting. May 2011
Various treatment approaches have had early trials or been proposed, but so far none with convincing evidence of usefulness or safety for treatment or prevention, including
brimonidine Brimonidine is a medication used to treat open-angle glaucoma, ocular hypertension, and rosacea. In rosacea it improves the redness. It is used as eye drops or applied to the skin. Common side effects when used in the eyes include itchiness, ...
, minocycline, curcumin,
glutathione Glutathione (GSH, ) is an antioxidant in plants, animals, fungi, and some bacteria and archaea. Glutathione is capable of preventing damage to important cellular components caused by sources such as reactive oxygen species, free radicals, pe ...
,
near infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from arou ...
light treatment,Wisconsin near infrared trial
and
viral vector Viral vectors are tools commonly used by molecular biologists to deliver genetic material into cells. This process can be performed inside a living organism (''in vivo'') or in cell culture (''in vitro''). Viruses have evolved specialized molecu ...
techniques. "Three person in vitro fertilization" is a proof-of-concept research technique for preventing mitochondrial disease in developing human fetuses. So far, viable macaque monkeys have been produced. But ethical and knowledge hurdles remain before use of the technique in humans is established.


Idebenone

Idebenone is a short-chain benzoquinone that interacts with the mitochondrial electron transport chain to enhance cellular respiration. When used in people with LHON, it is believed to allow electrons to bypass the dysfunctional complex I. Successful treatment with idebenone was initially reported in a small number of patients. Two large-scale studies have demonstrated the benefits of idebenone. The Rescue of Hereditary Optic Disease Outpatient Study (RHODOS) evaluated the effects of idebenone in 85 patients with LHON who had lost vision within the prior five years. In this study, the group taking idebenone 900 mg per day for 24 weeks showed a slight improvement in visual acuity compared to the placebo group, though the difference was not statistically significant. But patients taking idebenone were protected from further vision loss, whereas the placebo group had a steady decline in visual acuity. Further, people taking idebenone demonstrated preservation of color vision and persistence of the effects of idebenone 30 months after discontinuing therapy. A retrospective analysis of 103 LHON patients by Carelli et al. builds upon these results. This study highlighted that 44 subjects who were treated with idebenone within one year of onset of vision loss had better outcomes, and that these improvements persisted for years. Idebenone, combined with avoidance of smoke and limitation of alcohol intake, is the preferred treatment protocol for people with LHON. Idebenone doses are prescribed to be taken spaced out throughout the day, rather than all at once. For example, to achieve a dose of 900 mg per day, patients take 300 mg three times daily with meals. Idebenone is fat-soluble, and may be taken with a moderate amount of dietary fat in each meal to promote absorption. It is recommended that patients on idebenone also take vitamin C 500 mg daily to keep idebenone in its reduced form, as it is most active in this state.


Estrogen Replacement Therapy

Estrogen Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal ac ...
s have been shown to have a protective role in the pathogenesis of LHON. Experiments using LHON cybrids have demonstrated that the estrogen receptor localizes to the mitochondria where it directly mediates mitochondrial biogenesis. Estrogens upregulate the antioxidant enzyme superoxide dismutase 2 and mitochondrial DNA synthesis. These experiments helped to explain the mechanism behind the lower penetrance of disease among female carriers. While additional factors have been theorized, the protective role of estrogens appears to be a significant contributor. In addition to the experimental evidence, clinical data also points towards the protective role of estrogens. Penetrance among female carriers is substantially lower (between 3 and 8 to 1 male to female ratios depending on the mutation) while average age at onset is significantly higher. Multiple case series of various LHON pedigrees have described female carriers converting after menopause or cessation of hormone replacement therapies. Together, these form a shifting paradigm towards considering reduced estrogen states, such as menopause, as potential triggers of visual loss similar to smoking or excessive alcohol consumption.
Hormone replacement therapy Hormone replacement therapy (HRT), also known as menopausal hormone therapy or postmenopausal hormone therapy, is a form of hormone therapy used to treat symptoms associated with female menopause. These symptoms can include hot flashes, vaginal ...
(HRT) is emerging as an effective therapeutic target for female mutation carriers. In one recent case study where the affected female converted following cessation of HRT, idebenone, and HRT were given together. Visual acuity improved much faster than is typically expected. The patient's vision returned to 20/40 and 20/60 from 20/60 and 20/200 in the right and left eyes respectively after only one month and was back normal by 8 months compared to the months to years timeframe seen in most cases. While the balance between risks and benefits of HRT remains controversial, the decision to start HRT requires an individualized approach based on the patient's context. While not applicable for all post-menopausal women, prophylactic (and therapeutic) HRT should be considered in all female carriers of a known LHON mutation given the substantial risk of vision loss associated with menopause.


Epidemiology

In Northern European populations about one in 9,000 people carries one of the three primary LHON mutations. There is a
prevalence In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...
of between 1:30,000 to 1:50,000 in Europe. The LHON ND4 G11778A mutation is the primary mutation in most of the world, with 70% of Northern European cases and 90% of Asian cases. Due to a
Founder effect In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, us ...
, the LHON ND6 T14484C mutation accounts for 86% of LHON cases in
Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirte ...
, Canada. More than 50% of males with a mutation and more than 85% of females with a mutation never experience vision loss or related medical problems. The particular mutation type may predict the likelihood of
penetrance Penetrance in genetics is the proportion of individuals carrying a particular variant (or allele) of a gene (the genotype) that also express an associated trait (the phenotype). In medical genetics, the penetrance of a disease-causing mutation is t ...
, severity of illness and probability of vision recovery in the affected. As a rule of thumb, a woman who harbors a homoplasmic primary LHON mutation has a ~40% risk of having an affected son and a ~10% risk of having an affected daughter. Additional factors may determine whether a person develops the signs and symptoms of this disorder. Environmental factors such as smoking and alcohol use may be involved, though studies of these factors have produced conflicting results. Researchers are also investigating whether changes in additional genes, particularly genes on the X chromosome, contribute to the development of signs and symptoms. The degree of heteroplasmy, the percentage of mitochondria that have mutant
alleles An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chrom ...
, may play a role. Patterns of mitochondrial alleles called
haplogroup A haplotype is a group of alleles in an organism that are inherited together from a single parent, and a haplogroup (haploid from the el, ἁπλοῦς, ''haploûs'', "onefold, simple" and en, group) is a group of similar haplotypes that share ...
may also affect expression of mutations.


History

LHON was first described by the German ophthalmologist
Theodor Leber Theodor Karl Gustav von Leber (29 February 1840 – 17 April 1917) was a German ophthalmologist from Karlsruhe. Leber was a student of Hermann von Helmholtz (1821-1894) in Heidelberg, where he received his doctorate in 1862. He remained in Hei ...
(1840–1917) in 1871.Leber T. Ueber hereditaere und congenital angelegte sehnervenleiden (1871) Graefes Arch Clin Exp Ophthalmol. 17:249–291 In a paper, Leber described four families in which a number of young men had abrupt loss of vision in both eyes either simultaneously or sequentially. This disease was initially thought to be X-linked but was subsequently shown to be mitochondrial. The nature of the causative mutation was first identified in 1988 by Wallace ''et al.'' who discovered the
guanine Guanine () ( symbol G or Gua) is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine ( uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside is ...
(G) to
adenosine Adenosine (symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9- glycosidic bond. Adenosine is one of the four nucleoside building ...
(A) mutation at nucleotide position 11778 in nine families. This mutation converts a highly conserved
arginine Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) and both the am ...
to
histidine Histidine (symbol His or H) is an essential amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated –NH3+ form under biological conditions), a carboxylic acid group (which is in the ...
at
codon The genetic code is the set of rules used by living cells to translate information encoded within genetic material ( DNA or RNA sequences of nucleotide triplets, or codons) into proteins. Translation is accomplished by the ribosome, which links ...
340 in the
NADH dehydrogenase NADH dehydrogenase is an enzyme that converts nicotinamide adenine dinucleotide (NAD) from its reduced form (NADH) to its oxidized form (NAD+). Members of the NADH dehydrogenase family and analogues are commonly systematically named using the for ...
subunit 4 of complex I of the
mitochondria A mitochondrion (; ) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...
l respiratory chain. The other two mutations known to cause this condition were identified in 1991 (G to A point mutation at nucleotide position 3460) and 1992 (
thymidine Thymidine (symbol dT or dThd), also known as deoxythymidine, deoxyribosylthymine, or thymine deoxyriboside, is a pyrimidine deoxynucleoside. Deoxythymidine is the DNA nucleoside T, which pairs with deoxyadenosine (A) in double-stranded DNA. ...
(T) to
cytosine Cytosine () ( symbol C or Cyt) is one of the four nucleobases found in DNA and RNA, along with adenine, guanine, and thymine ( uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached ( ...
(C) mutation at nucleotide 14484). These three mutations account for over 95% of cases: the 11778 mutation accounts for 50-70% of cases, the 14484 mutation for 10-15% and the 3460 mutation for 8-25%.


Research

Human clinical trials are underway at GenSight Biologics (ClinicalTrials.gov # NCT02064569) and the University of Miami (ClinicalTrials.gov # NCT02161380) to examine the safety and efficacy of mitochondrial gene therapy in LHON. In these trials, participants affected by LHON with the G11778A mutation will have a virus expressing the functional version of ND4—the gene mutated in this variant of LHON—injected into one eye. A sham injection will be administered to the other eye for comparison. It is hypothesized that introduction of the viral vector may be able to rescue the function of the mutant gene. Preliminary results have demonstrated tolerability of the injections in a small number of subjects. Stealth BioTherapeutics is investigating the use of elamipretide (MTP-131), a mitochondrial protective agent, as a therapy for LHON. Elamipretide helps stabilize cardiolipin—an important component of mitochondrial inner membranes—and has been shown to reduce damaging reactive oxygen species in animal models.


See also

*
Amaurosis Amaurosis (Greek meaning ''darkening'', ''dark'', or ''obscure'') is vision loss or weakness that occurs without an apparent lesion affecting the eye. It may result from either a medical condition or excess acceleration, as in flight. The term is th ...
* Dominant optic atrophy *
Glaucoma Glaucoma is a group of eye diseases that result in damage to the optic nerve (or retina) and cause vision loss. The most common type is open-angle (wide angle, chronic simple) glaucoma, in which the drainage angle for aqueous humor, fluid withi ...
* Ischemic optic neuropathy * Optic atrophy *
Toxic and nutritional optic neuropathy Toxic and nutritional optic neuropathy is a group of medical disorders defined by visual impairment due to optic nerve damage secondary to a toxic substance and/or nutritional deficiency. The causes of these disorders are various, but they are lin ...


References


Further reading

* * *


External links


NCBI Genetic Testing Registry
{{Mitochondrial diseases Mitochondrial diseases Disorders of optic nerve and visual pathways