Peripapillary hyperreflective ovoid mass-like structures (PHOMS) in patients with acute Leber's hereditary optic neuropathy.

PURPOSE: Peripapillary hyperreflective ovoid mass-like structures (PHOMS) represent an optical coherence tomography (OCT) finding that has been characterized in different forms of pseudopapilledema. The aim of this study was to investigate the prevalence of PHOMS in patients affected by acute LHON using structural OCT, and to provide a detailed description of these findings. METHODS: Patients with a clinical and molecularly confirmed diagnosis of acute LHON (visual loss having occurred less than 6 months) were enrolled from the neuro-ophthalmology clinic at San Raffaele Scientific Institute. Patients had a complete ophthalmologic evaluation, including imaging with structural OCT. RESULTS: Our analysis included 16 patients (21 eyes-8 males and 8 females) with acute LHON. Structural OCT exhibited PHOMS in 12 eyes from 9 patients with a prevalence rate of 57.1%. In a subsequent topographical assessment in the peripapillary area, the most common location of PHOMS was the temporal region (12 out of 12 eyes), while the nasal region was affected in 2 eyes (16.7%). Considering the 12 eyes with PHOMS, mean ± SD temporal peripapillary RNFL thickness was 87.5 ± 28.4 microns. The temporal peripapillary RNFL thickness was significantly lower in eyes without PHOMS (63.7 ± 32.2 microns; P = 0.40). At the 12-month follow-up visit, PHOMS disappeared in 10 out of 12 eyes. CONCLUSIONS: Acute LHON eyes have PHOMS which are mainly confined to the temporal peripapillary sector. PHOMS may represent swelled retinal fibers that have herniated or are in stasis.

Functional Changes of Retinal Ganglion Cells and Visual Pathways in Patients with Chronic Leber's Hereditary Optic Neuropathy during One Year of Follow-up.

PURPOSE: To assess changes of retinal ganglion cells (RGCs) and visual pathways' function in patients with Leber's hereditary optic neuropathy (LHON) during 12 months of follow-up of the chronic phase. DESIGN: Retrospective case series. PARTICIPANTS: Twenty-two patients with LHON (mean age, 36.3±9.3 years) in the "chronic phase" of the disease, providing 42 eyes (LHON group) with different pathogenic mitochondrial DNA mutations (group 11778: 21 eyes; group 3460: 4 eyes; group 14484: 13 eyes; and group 14568: 4 eyes) were enrolled. Twenty-five age-similar healthy participants, providing 25 eyes, served as controls. METHODS: Pattern electroretinogram (PERG) and visual evoked potentials (VEP), in response to 60' and 15' checks visual stimuli, were recorded at baseline in all subjects and after 6 and 12 months of follow-up in patients with LHON. At baseline, in all LHON eyes for each PERG and VEP parameter (amplitude and implicit time), the 95% confidence limit (CL) of test-retest variability was calculated. The PERG and VEP mean values observed in LHON eyes were compared (1-way analysis of variance [ANOVA]) with those of controls. During the follow-up, the PERG and VEP differences observed with respect to baseline were evaluated by ANOVA. MAIN OUTCOME MEASURES: Changes of individual and mean absolute values of 60' and 15' PERG amplitude and VEP amplitude and implicit time at each time point compared with baseline values in the LHON group. RESULTS: At baseline, mean values of PERG and VEP parameters detected in the LHON group were significantly (P < 0.01) different with respect to control values. In the LHON group, at 6 and 12 months of follow-up, the majority of eyes showed unmodified (within 95% CL) PERG and VEP values, and mean absolute values of these measures were not significantly (P > 0.01) different from baseline values. CONCLUSIONS: In our untreated patients with chronic LHON, with different specific pathogenic mutations, RGCs and visual pathways function were not significantly modified during 12 months of follow-up. This should be considered in the disease natural history when attempts for treatments are proposed in chronic LHON.

Multifocal VEP provide electrophysiological evidence of predominant dysfunction of the optic nerve fibers derived from the central retina in Leber's hereditary optic neuropathy.

PURPOSE: To differentiate the bioelectrical cortical responses driven by axons from central and mid-peripheral retina in Leber's hereditary optic neuropathy (LHON) by using multifocal visual evoked potentials (mfVEP). METHODS: Seventeen genetically confirmed LHON patients (33.35 ± 8.4 years, 17 eyes) and 22 age-matched controls (C) (38.2 ± 6.0 years, 22 eyes) were studied by mfVEP and optical coherence tomography. MfVEP P1 implicit time (P1 IT, ms) and response amplitude density of the N1-P1 components (N1-P1 RAD, nV/deg(2)) of the second order binary kernel were measured for five concentric retinal areas between the fovea and mid-periphery: 0-20 degrees (R1 to R5). RESULTS: Mean mfVEP P1 ITs and N1-P1 RADs at all five foveal eccentricities were significantly different (p < 0.01) in LHON when compared to controls. In both groups, mean mfVEP responses obtained from R1 to R5 showed a progressive shortening of P1 ITs (linear fitting, LHON: r = -0.95; C: r = -0.98) and decrease of N1-P1 RADs (exponential fitting, LHON: r (2) = 0.94; C: r (2) = 0.93). The slope of the linear fitting between mean mfVEP P1 ITs in the two groups was about three times greater in LHON than in controls (LHON: y = -13.33x +182.03; C: y = -4.528x +108.1). MfVEP P1 ITs detected in R1 and R2 (0-5 degrees) were significantly correlated (p < 0.01) with the reduction of retinal nerve fiber layer thickness of the temporal quadrant. CONCLUSIONS: MfVEP identifies abnormal neural conduction along the visual pathways in LHON, discriminating a predominant involvement of axons driving responses from the central retina when compared to those serving the mid-peripheral retina.

AFG3L2 and ACO2-Linked Dominant Optic Atrophy: Genotype-Phenotype Characterization Compared to OPA1 Patients.

PURPOSE: Heterozygous mutations in the AFG3L2 gene (encoding a mitochondrial protease indirectly reflecting on OPA1 cleavage) and ACO2 gene (encoding the mitochondrial enzyme aconitase) are associated with isolated forms of Dominant Optic Atrophy (DOA). We aimed at describing their neuro-ophthalmological phenotype as compared with classic OPA1-related DOA. DESIGN: Cross-sectional study. METHODS: The following neuro-ophthalmological parameters were collected: logMAR visual acuity (VA), color vision, mean deviation and foveal threshold at visual fields, average and sectorial retinal nerve fiber layer (RNFL), and ganglion cell layer (GCL) thickness on optical coherence tomography. ACO2 and AFG3L2 patients were compared with an age- and sex-matched group of OPA1 patients with a 1:2 ratio. All eyes were analyzed using a clustered Wilcoxon rank sum test with the Rosner-Glynn-Lee method. RESULTS: A total of 44 eyes from 23 ACO2 patients and 26 eyes from 13 AFG3L2 patients were compared with 143 eyes from 72 OPA1 patients. All cases presented with bilateral temporal-predominant optic atrophy with various degree of visual impairment. Comparison between AFG3L2 and OPA1 failed to reveal any significant difference. ACO2 patients compared to both AFG3L2 and OPA1 presented overall higher values of nasal RNFL thickness (P = .029, P = .023), average thickness (P = .012, P = .0007), and sectorial GCL thickness. These results were confirmed also comparing separately affected and subclinical patients. CONCLUSIONS: Clinically, DOA remains a fairly homogeneous entity despite the growing genetic heterogeneity. ACO2 seems to be associated with an overall better preservation of retinal ganglion cells, probably depending on the different pathogenic mechanism involving mtDNA maintenance, as opposed to AFG3L2, which is involved in OPA1 processing and is virtually indistinguishable from classic OPA1-DOA.

Childhood-Onset Leber Hereditary Optic Neuropathy-Clinical and Prognostic Insights.

PURPOSE: To investigate the clinical and molecular genetic features of childhood-onset Leber hereditary optic neuropathy (LHON) to gain a better understanding of the factors influencing the visual outcome in this atypical form of the disease. DESIGN: Retrospective cohort study. METHODS: We retrospectively included 2 cohorts of patients with LHON with onset of visual loss before the age of 12 years from Italy and the United Kingdom. Ophthalmologic evaluation, including best-corrected visual acuity, orthoptic evaluation, slit-lamp biomicroscopy, visual field testing, and optical coherence tomography, was considered. Patients were classified based on both the age of onset and the pattern of visual loss. RESULTS: A total of 68 patients were stratified based on the age of onset of visual loss: group 1 (<3 years): 14 patients (20.6%); group 2 (≥3 to <9 years): 27 patients (39.7%); and group 3 (≥9 to ≤12 years): 27 patients (39.7%). Patients in group 2 achieved a better visual outcome than those in group 3. Patients in groups 1 and 2 had better mean deviation on visual field testing than those in group 3. The mean ganglion cell layer thickness on optical coherence tomography in group 2 was higher than those in groups 1 and 3. Patients were also categorized based on the pattern of visual loss as follows: Subacute Bilateral: 54 patients (66.7%); Insidious Bilateral: 14 patients (17.3%); Unilateral: 9 patients (11.1%); and Subclinical Bilateral: 4 patients (4.9%). CONCLUSIONS: Children who lose vision from LHON before the age of 9 years have a better visual prognosis than those who become affected in later years, likely representing a "form frustre" of the disease.

A Novel Hypothesis on Choroideremia-Manifesting Female Carriers: Could CHM In-Frame Variants Exert a Dominant Negative Effect? A Case Report.

Choroideremia is an X-linked recessive condition presenting in males, with progressive degeneration of retinal and choroidal tissues leading to progressive visual loss. Its pathological mechanism is due to alterations in the CHM gene that encodes for REP1, a protein required for prenylation of Rab by the Rab geranylgeranyl transferase (RGGT). Even though female carriers are predicted to be not affected by the disease, a wide phenotypic spectrum ranging from mild to severe cases has been reported in women. The reason why Choroideremia manifests in female carriers remains elusive. While X chromosome inactivation (XCI) skewing has been proposed as a leading putative mechanism, emerging evidence has shown that CHM could variably escape from XCI. We described a family with an initial clinical suspicion of Retinitis Pigmentosa in which a novel CHM pathogenic splicing variant was found by exome sequencing. The variant, initially found in the 63-year-old female presenting with impaired visual acuity and severe retinal degeneration, segregated in the 31-year-old daughter and the 37-year-old son, both presenting with fundus anomalies. mRNA studies revealed a shorter in-frame CHM isoform lacking exon 10. Molecular modeling of the ternary REP1/Rab/RGGT protein complex predicted significant impairing of REP1/Rab binding without alteration of REP1/RGGT interaction. We suggest that, in our female cases, the biallelic expression of CHM may have led to the production of both the mutant and wild type REP1. The mutant isoform, sequestrating RGGT, could reduce its available amount for Rab prenylation, thus exerting a dominant-negative effect. If confirmed with further studies and in large cohorts of female carriers, the here proposed molecular mechanism could help to explain the complexity of manifestation of Choroideremia in females.

Retinal nerve fiber layer thickness in dominant optic atrophy measurements by optical coherence tomography and correlation with age.

PURPOSE: To measure the retinal nerve fiber layer (RNFL) thickness by means of optical coherence tomography (OCT) in patients with dominant optic atrophy (DOA). DESIGN: Cross-sectional study. PARTICIPANTS: Thirty-three patients from 15 pedigrees with DOA harboring heterozygous mutations in the OPA1 gene and 43 healthy subjects were enrolled. METHODS: The RNFLs of DOA patients were studied by OCT and compared with those of 43 healthy subjects matched for age and optic nerve head (ONH) size. MAIN OUTCOME MEASURES: Retinal nerve fiber layer thickness. RESULTS: Dominant optic atrophy patients revealed a significant RNFL thickness reduction in all quadrants, with a preferential involvement of the temporal and inferior sectors. The progressive decline of RNFL thickness with age was similar to that observed in healthy subjects and was more evident in the 2 quadrants with higher residual amounts of fibers, that is, the superior and the inferior. The temporal quadrant was profoundly depleted of fiber so that the further rate of loss of microns per year is close to zero, whereas the nasal quadrant was spared the most by neurodegeneration. CONCLUSIONS: The present findings, taken in conjunction with the authors' previous description of small ONH size in DOA, strongly suggest that patients with this disease are born with fewer optic nerve axons and support the hypothesis that subsequent visual loss depends on further age-related loss of fibers, which also occurs in controls. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Male prevalence of acquired color vision defects in asymptomatic carriers of Leber's hereditary optic neuropathy.

PURPOSE: Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease resulting in loss of central vision and dyschromatopsia, caused by mitochondrial DNA point mutations. However, only a subset of the mutation carriers becomes affected, with a higher penetrance in males. This study was conducted to investigate chromatic losses in asymptomatic carriers of the LHON mutation. METHODS: Monocular chromatic discrimination was studied with the Cambridge Colour Test (CCT; Cambridge Research Systems, Ltd., Rochester, UK) along the protan, deutan, and tritan cone isolation axes in 46 LHON carriers (15 men) belonging to the same LHON maternal lineage and 74 age-matched control subjects (39 men). Inclusion criteria were absence of ophthalmic complaints and clear ocular media. A detailed neuro-ophthalmic examination was performed in all the LHON carriers. RESULTS: The differences in threshold between carriers and control subjects were significant for the three cone isolation axes at P < 0.0001. Sixty-five percent of the carriers had abnormal protan and/or deutan thresholds; some of those with higher thresholds also had elevated tritan thresholds (13%). The male thresholds were higher and more frequent than those of the women for the protan and deutan axes (ANOVA; P < 0.05), but not for tritan thresholds. In the most severe losses, the women had instances of diffuse defect whereas all the men displayed a red-green defect. CONCLUSIONS: Male LHON asymptomatic carriers had color vision losses with the red-green pattern of dyschromatopsia typical of patients affected with LHON, which includes elevation of tritan thresholds as well. This predominantly parvocellular (red-green) impairment is compatible with the histopathology of LHON, which affects mostly the papillomacular bundle. In contrast with male losses, female losses were less frequent and severe. These gender differences are relevant to understanding LHON pathophysiology, suggesting that hormonal factors may be of great importance.

Leber's hereditary optic neuropathy with childhood onset.

PURPOSE: To characterize the clinical features of childhood-onset Leber's hereditary optic neuropathy (LHON) as defined by a pathogenic mtDNA mutation and age at onset equal to or less than 10 years of age. METHODS: Fifty-six LHON Italian pedigrees including 180 affected individuals were reviewed, and 14 of 18 patients with childhood LHON were enrolled. LHON was classified as acute bilateral, acute unilateral, slowly progressive, and subclinical, according to disease features. All patients underwent a complete ophthalmic examination and optical coherence tomography (OCT), including retinal nerve fiber layer (RNFL) and optic nerve head analysis (ONH), and were compared with age- and optic disc size-matched control groups. RESULTS: The prevalence of childhood LHON in this case series was 11.5%. Five patients had an acute bilateral course, three an acute unilateral course with subclinical signs in the fellow eye, and six a slowly progressive course. Four of five acute patients with acute bilateral disease experienced visual recovery. Slowly progressive cases presented a better visual acuity and visual field outcome than acute cases. A significant diffuse reduction of RNFL was evident in children with acute LHON compared with the control group, whereas a significant reduction of the temporal quadrant was present in the slowly progressive and subclinical LHON cases. Acute LHON children had a smaller disc area and vertical disc diameter than did the control subjects. CONCLUSIONS: This study systematically characterized for the first time the subgroup of LHON with childhood onset. The peculiar clinical and anatomic features of childhood LHON offer insights for the understanding of LHON's pathophysiology as well as a basis for the differential diagnosis of visual loss in childhood.

Chromatic and luminance contrast sensitivities in asymptomatic carriers from a large Brazilian pedigree of 11778 Leber hereditary optic neuropathy.

PURPOSE: To determine whether asymptomatic 11778 LHON carriers demonstrated impairments in (1) chromatic red/green (R/G) and blue/yellow (B/Y) contrast sensitivity functions (CSF) and in (2) luminance contrast sensitivity functions in the spatial CSF (SCSF) and temporal CSF (TCSF) domains. METHODS: Twenty-five carriers (8 male, 17 female; 34.1 +/- 15.1 years of age) of homoplasmic 11778 LHON from the same well-described family and 30 age-matched controls (17 male, 13 female; 29.2 +/- 7.1 years of age) were tested in one eye, randomly selected. Of the 25 eyes tested, 18 had normal fundus, 5 had swelling and microangiopathy, and 2 had temporal pallor. The R/G and B/Y CSFs were obtained after equiluminance correction with bichromatic horizontal sinusoidal gratings at 0.3, 0.7, and 2 cycles per degree (cpd); the SCSFs were obtained with achromatic gratings at 0.3, 2, 6, and 12 cpd; and the TCSFs were obtained at 2, 10, 20, and 33 Hz with sinusoidal modulation of a 2.7 degrees field with a superimposed spatial Gabor function. RESULTS: Differences between carriers and controls were statistically significant for all spatial frequencies of chromatic and luminance SCSFs, but not for the TCSFs. R/G equiluminance settings of carriers differed from those of controls (P < 0.001), requiring higher luminance in the green; B/Y equiluminance settings were not statistically different in carriers and controls. Fundus findings did not correlate with CS results. CONCLUSIONS: Luminance and chromatic spatial CS losses that affected all tested spatial frequencies, are reported in LHON asymptomatic carriers with the mtDNA 11778 mutation. No losses were found in the temporal CSF. An intriguing finding is that the blue system is substantially spared in this LHON family. These represent subclinical visual impairments in otherwise asymptomatic LHON carriers.

Retinal nerve fiber layer evaluation by optical coherence tomography in unaffected carriers with Leber's hereditary optic neuropathy mutations.

PURPOSE: To study retinal nerve fiber layer (RNFL) thickness by optical coherence tomography (OCT) in unaffected carriers with Leber's hereditary optic neuropathy (LHON) mutations. DESIGN: Cross-sectional study. PARTICIPANTS: Sixty-six unaffected carriers (44 females and 22 males) were analyzed and compared with an age-matched control group of 70 patients (40 females and 30 males). The statistical analysis was performed after grouping both the patients and the control group on the basis of gender and, for unaffected carriers only, mitochondrial DNA mutation. METHODS: The Fast RNFL Thickness (3.4) scan acquisition protocol was used. MAIN OUTCOME MEASURE: Retinal nerve fiber layer thickness as measured by OCT. RESULTS: With respect to the control group, unaffected male carriers showed a thicker RNFL in the temporal and inferior quadrants and in the 360 degrees average measurement (P = 0.025, P = 0.03, and P = 0.018, respectively). These differences reached statistical significance in subjects carrying the 11778 mutation, whereas only a trend was detected in those with the 3460 mutation. Unaffected female carriers had an increased thickness in the temporal quadrant when compared with the control group (P = 0.003) and no differences in the other measurements. The increase in temporal sectors was statistically significant in females with the 11778 mutation, whereas a trend was detected in those with the 3460 mutation. CONCLUSIONS: A thickening of the temporal fibers was detected in all subgroups of unaffected carriers. This is the first evidence indicating the preferential involvement of the papillomacular bundle in subclinical LHON. This notion previously was based on the early loss of fibers from the temporal quadrant in acute LHON and the selective loss of small-caliber fibers at histopathology. Our study also revealed that males have a more diffuse involvement than females.

Retinal nerve fiber layer evaluation by optical coherence tomography in Leber's hereditary optic neuropathy.

PURPOSE: To study retinal nerve fiber layer (RNFL) thickness by optical coherence tomography (StratusOCT) in patients with Leber's hereditary optic neuropathy (LHON). DESIGN: Cross-sectional study. PARTICIPANTS AND/OR CONTROLS: Thirty-eight patients with LHON were analyzed and compared with an age-matched control group of 75 patients. Patients with LHON were classified as having early LHON (E-LHON, n = 8) when the duration of the disease was shorter than 6 months and atrophic LHON (A-LHON, n = 30) when the duration was longer than 6 months. METHODS: The fast RNFL thickness (3.4) scan acquisition protocol was used. MAIN OUTCOME MEASURE: Retinal nerve fiber layer thickness as measured by StratusOCT. RESULTS: Compared with the control group, eyes with E-LHON showed a thicker RNFL in the 360 degrees average measurement (P<0.01) and in the superior (P<0.01), nasal (P<0.05), and inferior quadrants (P<0.05); no significant changes were detected in the temporal quadrant. Eyes with A-LHON revealed a thinner RNFL in all measurements (P<0.001); the fibers of the nasal quadrant showed the lowest amount of reduction (38% vs. 42%-49.8% in the other quadrants). In cases with A-LHON and visual recovery, RNFL was significantly thicker in all measurements (P<0.001), except the temporal quadrant, with respect to A-LHON without visual recovery. CONCLUSIONS: On the basis of OCT data, the RNFL is thickened in E-LHON and severely thinned in A-LHON. RNFL is likely to be partially preserved in A-LHON with visual recovery. The temporal fibers (papillomacular bundle) are the first and most severely affected; the nasal fibers seem to be partially spared in the late stage of the disease.

Ophthalmologic findings in a large pedigree of 11778/Haplogroup J Leber hereditary optic neuropathy.

PURPOSE: To report the ophthalmologic characteristics of a newly identified seven-generation pedigree of 11778/Haplogroup J Leber hereditary optic neuropathy consisting of 328 living individuals, 111 of whom are maternally related. DESIGN: Observational population cohort study. METHODS: This prospective study of a large Brazilian Leber hereditary optic neuropathy pedigree was carried out as a field investigation in Brazil. We describe the ophthalmologic findings of 192 eyes from 96 maternally related individuals of this pedigree. Spouses were used as control subjects. We conducted comprehensive neuro-ophthalmologic examinations with psychophysical tests, Humphrey visual fields, and fundus photographs. We also correlated the ophthalmologic findings with the previously published epidemiologic assessment of risk factors. RESULTS: We examined 76 carriers and 20 affected individuals. The affected individuals showed severe disease with a mean visual acuity of 2.04 logarithm of the minimal angle of resolution and without evidence of recovery. All the affected individuals showed diffuse optic atrophy with a cup-to-disk ratio greater than 0.5 in 55% of cases. Moreover, among Affected individuals, smokers had a poorer visual acuity (P =.002). Among carriers there were several subclinical abnormalities, including microangiopathy, swelling of nerve fibers, and visual field abnormalities that did not correlate with tobacco or alcohol consumption. CONCLUSIONS: Our results demonstrate a significant influence of environmental risk factors, particularly smoking, for developing Leber hereditary optic neuropathy and for the severity of its clinical expression. However, smoking did not correlate with the subclinical abnormalities detected in carriers. Moreover, subclinical abnormalities were equally distributed between gender.

Retinal function and neural conduction along the visual pathways in affected and unaffected carriers with Leber's hereditary optic neuropathy.

PURPOSE: We assessed retinal ganglion cell (RGC) function, and established a correlation between the neural conduction along the visual pathways and the retinal involvement in Leber's hereditary optic neuropathy (LHON). METHODS: A total of 39 individuals carrying a LHON mutation (mean age, 33.35 ± 8.4 years), LHON-unaffected (LU, 22 eyes) or LHON-affected (LA, 17 eyes), underwent visual acuity and visual field examinations. A total of 22 age-similar normal subjects (mean age, 38.2 ± 6.0 years) served as controls. In all subjects, simultaneous pattern electroretinograms (PERGs) and visual evoked potentials (VEPs) were recorded in response to 60-minute (60') and 15-minute (15') checkerboard stimuli. RESULTS: When compared to controls, LU eyes did not show any statistically significant difference in 60' and 15' VEP P100 implicit times (ITs), VEP N75-P100 amplitudes, and 60' PERG P50 ITs, whereas 15' PERG P50-N95 amplitudes were significantly (P < 0.01) reduced. When compared to control and LU eyes, LA eyes showed significant differences in PERG and VEP ITs, and amplitudes with both stimulations (60' and 15' checks). No significant correlations between PERG and VEP parameters were found in LU eyes, while in LA eyes, PERG P50 and VEP P100 ITs correlated significantly only when using 60' checks. CONCLUSIONS: The LHON-unaffected eyes showed a retinal dysfunction detected by abnormal PERG responses that was not associated with changes along the visual pathways assessed by normal VEP responses. In LA eyes, the impaired neural conduction recorded by VEPs in response to larger (60' VEP responses) and smaller (15' VEP responses) checks were associated and not associated, respectively, with the detected retinal dysfunction.

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.

Association of optic disc size with development and prognosis of Leber's hereditary optic neuropathy.

PURPOSE: To study the optic nerve head (ONH) morphology of patients with Leber's hereditary optic neuropathy (LHON) in a large family from Brazil carrying the 11778/ND4 mutation and in a case series of unrelated Italian families bearing different mitochondrial DNA (mtDNA) pathogenic mutations. METHODS: Enrolled in the study were 15 LHON-affected patients (LHON-affected) and 45 LHON unaffected mutation carriers (LHON carriers) belonging to the previously reported Brazilian SOA-BR LHON pedigree and 56 LHON-affected and 101 LHON carriers from 45 unrelated LHON Italian pedigrees molecularly defined. The LHON-affected were subgrouped according to the extent of visual recovery. All individuals underwent optic nerve head (ONH) analysis by optical coherence tomography. RESULTS: In the Brazilian sample, the mean optic disc area was significantly larger in LHON carriers than in the control group (P=0.002). In the Italian sample, the mean optic disc area and vertical disc diameter were significantly higher in LHON carriers than in both LHON-affected (respectively, P=0.008 and P<0.001) and control subjects (P<0.001 in both cases). The LHON-affected with visual recovery had a significantly larger vertical disc diameter when compared with those without visual recovery (P=0.03). CONCLUSIONS: The results, revealing that the ONH size is larger in LHON carriers than in LHON-affected, suggest a protective role for this anatomic trait. Such a hypothesis is reinforced by the observation that, among the LHON-affected, larger discs correlated with visual recovery and better visual outcome. The findings may be relevant for prognosis and provide a mechanism for identifying nuclear-modifying genes implicated in the variability of penetrance in LHON.