Evaluation of fixation pattern and reading ability in patients with Leber hereditary optic neuropathy.

BACKGROUND: Leber hereditary optic neuropathy (LHON) is characterized by progressive loss of central vision leading to impaired reading ability. The aim of this study was to evaluate sensory adaptation and reading ability in LHON patients. METHODS: This prospective pilot study included 12 male patients with a clinical diagnosis and a positive genetic analysis of LHON, who matched the inclusion criteria of a central scotoma on visual field testing and the use of magnifying aids to read. Examination included best-corrected visual acuity, magnification need, reading speed, and evaluation of fixation by corneal reflexes and by Rodenstock scanning laser ophthalmoscope (SLO). Central scotoma was assessed by conventional perimetry (Tübingen Automated Perimeter) and microperimetry (NIDEK MP1). RESULTS: Mean magnification need was 13.2 ± 7.3-fold (range: 2- to 25-fold). Mean reading speed was 53 ± 18 words per minute (WPM) (range: 24-85 WPM). With automated perimetry, all patients showed central scotomas with a mean radius of 13° ± 7° (range: 1°-30°) in the better eye. Microperimetry in all patients showed fenestrated central scotomas. Eccentric fixation with a preferred retinal locus (PRL) was detected with SLO examination and microperimetry correlated well in 11 of 12 patients. The SLO results showed no systematic pattern in the placement of the PRL; however, 7 of 12 patients (58%) placed their PRL in an unfavorable location left or below the fovea. In 8 of 12 patients, fixation was unstable. Between reading speed and central scotoma size, there was a statistically significant negative correlation (P = 0.021, r = -0.65). CONCLUSIONS: The percentage of unfavorable PRL locations was extremely high compared with other disorders with central scotomas. Unstable fixation and fenestrated central scotomas led to difficulties in reading. Early rehabilitation and, if necessary, eccentric viewing training should be considered in LHON patients.

Encephalopathic Susac's Syndrome associated with livedo racemosa in a young woman before the completion of family planning.

BACKGROUND: Susac's Syndrome (SS) consists of the triad of encephalopathy, branch retinal artery occlusions (BRAO) and hearing loss (HL). Histopathologically, SS is characterised by a microangiopathy, and some observations suggest that an immune-mediated damage of endothelial cells might play a role. These findings also implicate a similarity between SS and other autoimmune diseases, most notably juvenile dermatomyositis (JDM). However, SS and JDM are commonly thought to affect distinct and non-overlapping sets of organs, and it is currently not clear how these specificities arise. Moreover, in the absence of clinical trials, some authors suggest that therapeutic approaches in SS should rely on the model of other autoimmune diseases such as JDM. CASE PRESENTATION: Here, we report a case of SS in a 32-year-old pregnant woman. She initially was admitted to the hospital with subacute severe encephalopathy and multifocal neurologic signs. As cranial magnetic resonance imaging (MRI) revealed multifocal white matter lesions including the corpus callosum, erroneously a diagnosis of multiple sclerosis (MS) was made, and intravenous methylprednisolone (IVMP) therapy was initiated. A few days later, an exanthema appeared on the trunk and extremities, which was diagnosed as livedo racemosa (LR). Several weeks later, the patient was readmitted to the clinic with an obscuration of her left visual hemifield and a bilateral HL. Ophthalmologic examination revealed extensive ischemic damage to both retinae. Now the correct diagnosis of SS was established, based on the above triad of clinical symptoms in conjunction with typical MRI and fundoscopic findings. When SS was diagnosed, the standard therapy with intravenous cyclophosphamide (IVCTX) was not instituted because of a significant risk of permanent infertility. Instead, sustained control of disease activity could be achieved with a therapeutic regime combining prednisolone, intravenous immunoglobulins (IVIG), mycophenylate mofetil (MM), and methotrexate (MTX). CONCLUSIONS: An association with LR has only been described in very few cases of SS before and further underlines the pathogenetic relationship between SS and other autoimmune diseases such as JDM. In young women with SS and the desire for a child the combination of MM and MTX may represent a reasonable alternative to IVCTX.

A novel heterozygous OPA3 mutation located in the mitochondrial target sequence results in altered steady-state levels and fragmented mitochondrial network.

BACKGROUND: Mutations in OPA3 have been reported in patients with autosomal dominant optic atrophy plus cataract and Costeff syndrome. Here, we report the results of a comprehensive study on OPA3 mutations, including the mutation spectrum and its prevalence in a large cohort of OPA1-negative autosomal dominant optic atrophy (ADOA) patients, the associated clinical phenotype and the functional characterisation of a newly identified OPA3 mutant. METHODS: Mutation analysis was carried out in a patient cohort of 121 independent ADOA patients. To characterise a novel OPA3 mutation, we analysed the mitochondrial import, steady-state levels and the mitochondrial localisation of the mutated protein in patients' fibroblasts. Furthermore, the morphology of mitochondria harbouring the mutated OPA3 was monitored. RESULTS: We identified four independent cases (representing families with multiple affected members) with OPA3 mutations. Besides the known p.Q105E mutation, we observed a novel insertion, c.10_11insCGCCCG/p.V3_G4insAP which is located in the mitochondrial presequence. Detailed functional analysis of mitochondria harbouring this novel mutation demonstrates a fragmented mitochondrial network with a decreased mitochondrial mass in patient fibroblasts. In addition, quantification of the OPA3 protein reveals decreased steady-state levels of the mutant protein compared with the native one. Comparison of the clinical phenotypes suggests that OPA3 mutations can additionally evoke hearing loss and by that extend the clinical manifestation of OPA3-associated optic atrophy. This finding is supported by expression analysis of OPA3 in murine cochlear tissue. CONCLUSIONS: In summary, our study provides new insights into the clinical spectrum and the pathogenesis of dominant optic atrophy caused by mutations in the OPA3 gene.

Rare primary mitochondrial DNA mutations and probable synergistic variants in Leber's hereditary optic neuropathy.

BACKGROUND: Leber's hereditary optic neuropathy (LHON) is a maternally inherited blinding disorder, which in over 90% of cases is due to one of three primary mitochondrial DNA (mtDNA) point mutations (m.11778G>A, m.3460G>A and m.14484T>C, respectively in MT-ND4, MT-ND1 and MT-ND6 genes). However, the spectrum of mtDNA mutations causing the remaining 10% of cases is only partially and often poorly defined. METHODOLOGY/PRINCIPAL FINDINGS: In order to improve such a list of pathological variants, we completely sequenced the mitochondrial genomes of suspected LHON patients from Italy, France and Germany, lacking the three primary common mutations. Phylogenetic and conservation analyses were performed. Sixteen mitochondrial genomes were found to harbor at least one of the following nine rare LHON pathogenic mutations in genes MT-ND1 (m.3700G>A/p.A132T, m.3733G>A-C/p.E143K-Q, m.4171C>A/p.L289M), MT-ND4L (m.10663T>C/p.V65A) and MT-ND6 (m.14459G>A/p.A72V, m.14495A>G/p.M64I, m.14482C>A/p.L60S, and m.14568C>T/p.G36S). Phylogenetic analyses revealed that these substitutions were due to independent events on different haplogroups, whereas interspecies comparisons showed that they affected conserved amino acid residues or domains in the ND subunit genes of complex I. CONCLUSIONS/SIGNIFICANCE: Our findings indicate that these nine substitutions are all primary LHON mutations. Therefore, despite their relative low frequency, they should be routinely tested for in all LHON patients lacking the three common mutations. Moreover, our sequence analysis confirms the major role of haplogroups J1c and J2b (over 35% in our probands versus 6% in the general population of Western Europe) and other putative synergistic mtDNA variants in LHON expression.

Solving a 50 year mystery of a missing OPA1 mutation: more insights from the first family diagnosed with autosomal dominant optic atrophy.

BACKGROUND: Up to the 1950s, there was an ongoing debate about the diversity of hereditary optic neuropathies, in particular as to whether all inherited optic atrophies can be ascribed to Leber's hereditary optic neuropathy (LHON) or represent different disease entities. In 1954 W. Jaeger published a detailed clinical and genealogical investigation of a large family with explicit autosomal dominant segregation of optic atrophy thus proving the existence of a discrete disease different from LHON, which is nowadays known as autosomal dominant optic atrophy (ADOA). Since the year 2000 ADOA is associated with genomic mutations in the OPA1 gene, which codes for a protein that is imported into mitochondria where it is required for mitochondrial fusion. Interestingly enough, the underlying mutation in this family has not been identified since then. RESULTS: We have reinvestigated this family with the aim to identify the mutation and to further clarify the underlying pathomechanism. Patients showed a classical non-syndromic ADOA. The long term deterioration in vision in the two teenagers examined 50 years later is of particular note 5/20 to 6/120. Multiplex ligation probe amplification revealed a duplication of the OPA1 exons 7-9 which was confirmed by long distance PCR and cDNA analysis, resulting in an in-frame duplication of 102 amino acids. Segregation was verified in 53 available members of the updated pedigree and a penetrance of 88% was calculated. Fibroblast cultures from skin biopsies were established to assess the mitochondrial network integrity and to qualitatively and quantitatively study the consequences of the mutation on transcript and protein level. Fibroblast cultures demonstrated a fragmented mitochondrial network. Processing of the OPA1 protein was altered. There was no correlation of the OPA1 transcript levels and the OPA1 protein levels in the fibroblasts. Intriguingly an overall decrease of mitochondrial proteins was observed in patients' fibroblasts, while the OPA1 transcript levels were elevated. CONCLUSIONS: The thorough study of this family provides a detailed clinical picture accompanied by a molecular investigation of patients' fibroblasts. Our data show a classic OPA1-associated non-syndromic ADOA segregating in this family. Cell biological findings suggest that OPA1 is regulated by post-translational mechanisms and we would like to hypothesize that loss of OPA1 function might lead to impaired mitochondrial quality control. With the clinical, genetic and cell biological characterisation of a family described already more than 50 years ago, we span more than half a century of research in optic neuropathies.

Inner retinal contributions to the multifocal electroretinogram: patients with Leber's hereditary optic neuropathy (LHON). Multifocal ERG in patients with LHON.

In this study we examine the multifocal electroretinogram (mfERG) recorded from patients suffering from Leber's hereditary optic neuropathy (LHON), a degeneration of the ganglion cell and nerve fibre layers of the retina. We compared the mfERGs recorded from 11 patients with LHON, to those from 11 control subjects. The pattern ERG (PERG) was additionally performed with 9 of the patients. MfERGs were recorded and analysed using the VERIS 3.01 system with a stimulus of 103 equal-sized hexagons. For analysis, hexagons were grouped according to distance from the optic nerve head (ONH) and according to distance from the fovea. Two significant differences were found between the waveforms of the two groups: In the first order kernel, the control group showed a component around 34 ms that decreased with distance from the ONH. This component was reduced in the LHON group of subjects. In the second order (first slice) kernel, the patient group was missing features that decrease with distance from the fovea in the control group. PERG amplitudes showed a significant correlation with the amplitude of the second order mfERG kernel. The results show that the damage to ganglion cells and nerve fibres caused by LHON can be detected in mfERG recordings and indicate that activity from the inner retina can contribute significantly to first and second order waveforms.

Detecting color vision in a malingerer.

A patient describing himself as totally color blind was ordered by the judicial system to have his color vision investigated in order to establish his suitability for military service. Basic clinical (Farnsworth Panel D-15, Moreland and Rayleigh anomaloscope equations), electroretinographic (ERG) and psychophysical techniques (spectral sensitivities) were applied to determine the extent of his color discrimination performance and cone function. These standard procedures were complemented by a test for cone interaction (transient tritanopia) and by newly developed cone-isolating flicker large-field ERG recordings. The patient's data consistently indicate the function as well as the functional interaction of the middle-wavelength-sensitive (M-) and the short-wavelength-sensitive (S-) cones. But the function of the long-wavelength-sensitive (L-) cones was completely absent. Hence the patient was correctly demonstrated to be a protanope. This study establishes that standard classical procedures, in combination with newly developed and easy to apply psychophysical and ERG ones, which can be reliably used to assess true color discrimination performance, in difficult cases of malingering.

Leber's hereditary optic neuropathy: clinical and molecular genetic results in a patient with a point mutation at np T11253C (isoleucine to threonine) in the ND4 gene and spontaneous recovery.

BACKGROUND: Mitochondrial DNA mutations at nucleotide position (np) 3460 in the ND1 gene, np 11778 in the ND4 gene, and np 14484 in the ND6 gene are commonly considered to be associated with the clinical features of LHON and account for the majority of LHON cases. Here we report the clinical and molecular genetic findings of a LHON patient with a new mitochondrial DNA mutation at np 11253 in the ND4 gene and spontaneous recovery. METHODS: The clinical examination consisted of visual acuity measurements, visual field testing, and ophthalmoscopy over a period of 14 years. Total lymphocyte DNA was analyzed for all common LHON mutations. Because the LHON patient did not harbor any of the common or recently described rare LHON mutations, we performed a sequence analysis of the whole mitochondrial genome. RESULTS: The patient exhibited typical clinical features of LHON. Molecular genetic analysis did not reveal any of the common LHON mutations. Sequence analysis of the mtDNA of the patient and his unaffected sister and niece was performed and showed a T to C missense mutation at np 11253 in the ND4 gene, leading to a replacement of an evolutionary highly conserved isoleucine by a threonine residue. This mutation introduces a polar group into a hydrophobic domain of the protein and induces a significant change in hydrophobicity of the peptide sequence. The mutation was not found among 100 controls. CONCLUSION: The fact that the new mutation at np 11253 is found within a highly conserved region and was not present in any controls implies that this mutation is responsible for LHON in this patient. Interestingly, this point mutation has formerly been reported in the mitochondria of the substantia nigra in an unrelated patient with proven Parkinson's disease.

Confirmation of the 14568 mutation in the mitochondrial ND6 gene as causative in Leber's hereditary optic neuropathy.

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disorder characterized by a rapid bilateral loss of central vision. The majority of patients have one of three mutations in the mitochondrial DNA. In order to identify the genetic cause of the disease in a family with two affected individuals without any of the three primary LHON mutations, we have sequenced the complete mitochondrial genome. Sequence analysis revealed a point mutation at position 14568 in the mitochondrial ND6 gene that changes a conserved methionine residue to isoleucine. This mutation has been previously suggested to be of pathogenic significance and has not been detected in any controls. This case confirms the pathogenicity of this mutation. It is the seventh mutation in the ND6 gene leading to LHON. All seven identified mutations in the ND6 gene lie within the evolutionarily most conserved region of the ND6 gene in a hydrophobic pocket making it a hot spot for the disease. This clustering of mutations may help to understand the disease mechanism of LHON.

Sequence analysis of the complete mitochondrial genome in patients with Leber's hereditary optic neuropathy lacking the three most common pathogenic DNA mutations.

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disorder characterized by central vision loss in young adults. The majority of LHON cases around the world are associated with mutations in the mitochondrial genome at nucleotide positions (np) 3460, 11,778, and 14,484. Usually, these three mutations are screened in suspected LHON patients. The result is important not only in respect to the diagnosis but also as different LHON mutations lead to variations in expression, severity, and recovery of the disease. There are, however, a significant number of patients without any of these primary mutations. In these situations, genetic counselling of a patient and his family can be difficult. We sequenced the complete mitochondrial DNA (mtDNA) in 14 LHON patients with the typical clinical features but without a primary mtDNA mutation to evaluate the potential of extensive mutation screening for clinical purposes. Our results suggest to include the mutation at np 15,257 in a routine screening as well as the ND6 gene, a hot spot for LHON mutations. Screening for the secondary LHON mutations at np 4216 and np 13,708 may also help in making the diagnosis of LHON as these seem to modify the expression of LHON mutations. Although they do not allow to prove the clinical diagnosis, their presence increases the probability of LHON. Sequencing the complete mitochondrial genome can reveal novel and known rare disease causing mutations. However, considering the effort it adds little value for routine screening.

A mutational hot spot in the mitochondrial ND6 gene in patients with Leber's hereditary optic neuropathy.

BACKGROUND: Leber's hereditary optic neuropathy (LHON) is a maternally inherited disorder characterized by rapid bilateral loss of central vision. Most patients harbor one of three mutations in the mitochondrial DNA. In order to identify the genetic cause of the disease in one LHON patient without any of the three primary mutations, we sequenced the mitochondrial genome. METHODS: Ophthalmological examination was performed in the affected person and his unaffected relatives. The complete mitochondrial protein coding region was sequenced in the patient. RESULTS: Clinical examination of the affected 10-year-old Turkish boy showed typical features of LHON. Peripapillary microangiopathy was also seen in relatives of the maternal line. Sequence analysis revealed a point mutation at position 14482 in the mitochondrial ND6 gene that changes a conserved methionine residue to isoleucine. A mutation at this nucleotide position has been previously suggested to be of pathogenic significance and has not been detected in any controls. CONCLUSIONS: We have identified that the mutation at nucleotide position 14482 which is the eight mutation in the ND6 gene that causes LHON, making this gene a hot spot for the disease. All eight identified mutations in the ND6 gene lie within the evolutionarily most conserved region of the ND6 gene in a hydrophobic pocket. This may help in understanding the pathomechanism of LHON.