Age-dependent retinal neuroaxonal degeneration in children and adolescents with Leber hereditary optic neuropathy under idebenone therapy

BACKGROUND

The aim of this study was to investigate the neuroretinal structure of young patients with Leber Hereditary Optic Neuropathy (LHON).

METHODS

For this retrospective cross-sectional analysis, the peripapillary retinal nerve fiber layer (pRNFL) thickness and the macular retinal layer volumes were measured by optical coherence tomography. Patients aged 12 years or younger at disease onset were assigned to the childhood-onset (ChO) group and those aged 13 to 16 years to the early teenage-onset (eTO) group. All patients received treatment with idebenone. The same measurements were repeated in age-matched control groups with healthy subjects.

RESULTS

The ChO group included 11 patients (21 eyes), and the eTO group 14 patients (27 eyes). Mean age at onset was 8.6±2.7 years in the ChO group and 14.8±1.0 years in the eTO group. Mean best-corrected visual acuity (BCVA) was 0.65±0.52 logMAR in the ChO group and 1.60±0. 51 logMAR in the eTO group (p<0.001). Reduced pRNFL was evident in the eTO group compared to the ChO group (46.0±12.7 μm vs. 56.0±14.5 μm, p=0.015). Additionally, a significantly lower combined ganglion cell and inner plexiform layer volume was found in the eTO compared to the ChO group (0.266±0.0027 mm³ vs. 0.294±0.033 mm³ , p=0.003). No difference in these parameters was evident between the age-matched control groups.

CONCLUSION

Less neuroaxonal tissue degeneration was observed in ChO LHON than in eTO LHON, a finding that may explain the better functional outcome of ChO LHON.

Leber hereditary optic neuropathy presenting as bilateral visual loss and white matter disease

Leber hereditary optic neuropathy (LHON) is a rare maternally inherited mitochondrial disorder that typically affects young male adults in their second and third decades of life. It usually manifests as painless, subacute, progressive, bilateral vision loss, with more than 90% of affected individuals losing their vision before age 50. Compared with other diseases that cause optic neuritis (multiple sclerosis or neuromyelitis optica spectrum disorders), LHON has worsening visual function in the first 6-12 months of disease progression, is predominantly male, the optic nerve is affected bilaterally from onset, there is no gadolinium enhancement on MRI, no response to disease-modifying therapy, and there is a family history of mutation in mitochondrial DNA. In this article, we describe an interesting and challenging case of LHON due to a homoplasmic variant in the MT -CO3 gene that was initially misdiagnosed as a monophasic demyelinating disorder (clinically isolated syndrome vs acute disseminated encephalomyelitis vs neuromyelitis optica spectrum disorders).

COINCIDENCE OF IDIOPATHIC INTRACRANIAL HYPERTENSION AND LEBER HEREDITARY OPTIC NEUROPATHY. A CASE REPORT

GOAL

This paper describes a case of a long-term monitoring of a patient with optic nerve swelling on the ocular background (papilledema), accompanied by symptoms of intracranial hypertension, on whom a genetic examination was performed as part of differential diagnosis, confirming Leber Hereditary Optic Neuropathy with the m.3460G&gt;A mutation. Casuistry: During the examination of a 5-year-old patient after an alleged head injury at a bouncy castle, an optic nerve papilla with unclear boundaries was described on the ocular background of both eyes. Neurological examination, including brain Magnetic Resonance Imaging, was indicated to rule out possible intracranial hypertension. Both examinations yielded a finding within the norm. After eight years of regular follow-up, the patient attended to our clinic with acute problems in terms of sudden visual impairment during baseball training. The performed eye examination revealed a deterioration of the vision of the right eye on counting fingers to 50 cm, vision of the left eye to 0.4 naturally, a slowed photoreaction of the right pupil, prominent optic nerve papilla with unclear boundaries on both eyes, dilated and more coiled vessels with a crossing phenomenon, the retinal periphery shows no focal changes. Due to the swelling of the papilla, acute deterioration of the vision and the suspected intracranial hypertension, the patient was immediately referred for neurological examination and subsequent hospitalization. There, the patient underwent computer tomography of the brain, venography of the dural venous sinuses and an initial laboratory examination that showed no pathology. There was increasing headache, nausea and vomiting throughout the period. A lumbar puncture was performed. The cerebrospinal fluid pressure before sampling was 285 mmH2O and 100 mmH2O after sampling. The biochemistry of the fluid was normal with negative microbiology. Evoked visual potentials had bilaterally prolonged latencies, which corresponds to optic nerve compression. An ophthalmological examination ruled out a drusen papilla. Using Optical Coherence Tomography, a 600 &#956;m edema was detected. The patient underwent two relieving lumbar punctures, which led to a subjective improvement without objective improvement. Finally, the neurosurgeon referred the patient for ventriculoperitoneal drainage. Due to the impaired vision and lack of response to the therapy induced, a genetic test was performed, which confirmed Leber Hereditary Optic Neuropathy with the mutation of m.3460G&gt;A.

CONCLUSION

Despite the substantially improved identification of the Leber Hereditary Optic Neuropathy, the diagnosis may still be significantly delayed. The variability of initial findings, the rare incidence of the disease and few well-defined symptoms of the disease lead to significant diagnostic difficulties and late commencement of treatment. It is not possible to say whether there was a coincidence of IIH and LHON or whether the signs of IIH are a possible concomitant of the acute phase of LHON.

Efficacy and Safety of Intravitreal Gene Therapy for Leber Hereditary Optic Neuropathy Treated within 6 Months of Disease Onset

PURPOSE

To evaluate the efficacy of a single intravitreal injection of rAAV2/2-ND4 in subjects with visual loss from Leber hereditary optic neuropathy (LHON).

DESIGN

RESCUE is a multicenter, randomized, double-masked, sham-controlled, phase 3 clinical trial.

PARTICIPANTS

Subjects with the m.11778G>A mitochondrial DNA mutation and vision loss ≤6 months from onset in 1 or both eyes were included.

METHODS

Each subject's right eye was randomly assigned (1:1) to treatment with rAAV2/2-ND4 (single injection of 9 × 10¹⁰ viral genomes in 90 μl) or to sham injection. The left eye received the treatment not allocated to the right eye.

MAIN OUTCOME MEASURES

The primary end point was the difference of the change from baseline in best-corrected visual acuity (BCVA) between rAAV2/2-ND4-treated and sham-treated eyes at week 48. Other outcome measures included contrast sensitivity, Humphrey visual field perimetry, retinal anatomic measures, and quality of life. Follow-up extended to week 96.

RESULTS

Efficacy analysis included 38 subjects. Mean age was 36.8 years, and 82% were male. Mean duration of vision loss at time of treatment was 3.6 months and 3.9 months in the rAAV2/2-ND4-treated eyes and sham-treated eyes, respectively. Mean baseline logarithm of the minimum angle of resolution (logMAR) BCVA (standard deviation) was 1.31 (0.52) in rAAV2/2-ND4-treated eyes and 1.26 (0.62) in sham-treated eyes, with a range from -0.20 to 2.51. At week 48, the difference of the change in BCVA from baseline between rAAV2/2-ND4-treated and sham-treated eyes was -0.01 logMAR (P = 0.89); the primary end point of a -0.3 logMAR (15-letter) difference was not met. The mean BCVA for both groups deteriorated over the initial weeks, reaching the worst levels at week 24, followed by a plateau phase until week 48, and then an improvement of +10 and +9 Early Treatment Diabetic Retinopathy Study letters equivalent from the plateau level in the rAAV2/2-ND4-treated and sham-treated eyes, respectively.

CONCLUSIONS

At 96 weeks after unilateral injection of rAAV2/2-ND4, LHON subjects carrying the m.11778G>A mutation treated within 6 months after vision loss achieved comparable visual outcomes in the injected and uninjected eyes.

"Eye genetics at the fork in the road" 2017 Franceschetti Lecture, Leeds UK

Inherited retinal diseases - a disparate group of eye disorders with over 200 known genetic causes - are now the leading cause of blindness in working-age adults in developed countries. Until recently there was no cure for genetic eye diseases. After over a century of defining inherited retinal diseases with their phenotypes, and then several decades of discovering associated genes and their mutations, we now have gene therapy, stem cell therapy, predictive DNA testing and a revolution in adaptive computer technology. With the explosion of expensive treatment options, we need to consider whether finite resources should go towards treatment, prevention or rehabilitation or an amalgamation of all three. In addition, although evidence-based medicine is the goal, how do we direct our desperate patients towards genuine clinical trials and away from quackery? How do we provide scientifically valid treatments for eye diseases too rare to run proper trials and then capture the results of "off label treatments"?

Leber Hereditary Optic Neuropathy and Longitudinally Extensive Transverse Myelitis

Leber Hereditary Optic Neuropathy is an inherited optic neuropathy caused by mitochondrial DNA point mutations leading to sudden, painless loss of vision. We report a case of an 8-year-old boy presenting with a radiological phenotype of longitudinally extensive transverse myelitis on a background of severe visual impairment secondary to Leber Hereditary Optic Neuropathy (LHON). He was found to have dual mitochondrial DNA mutations at 14484 (MTND6 gene) and 4160 (MTND1 gene) in a family with a severe form of LHON characterised by not only an unusually high penetrance of optic neuropathy, but also severe extra-ocular neurological complications. The m.14484T>C mutation is a common LHON mutation, but the m.4160T>C mutation is to our knowledge not reported outside this family and appears to drive the neurological manifestations. To our knowledge there have been no previous reports of spinal cord lesions in children with LHON.

Respiratory complex III dysfunction in humans and the use of yeast as a model organism to study mitochondrial myopathy and associated diseases

The bc1 complex or complex III is a central component of the aerobic respiratory chain in prokaryotic and eukaryotic organisms. It catalyzes the oxidation of quinols and the reduction of cytochrome c, establishing a proton motive force used to synthesize adenosine triphosphate (ATP) by the F1Fo ATP synthase. In eukaryotes, the complex III is located in the inner mitochondrial membrane. The genes coding for the complex III have a dual origin. While cytochrome b is encoded by the mitochondrial genome, all the other subunits are encoded by the nuclear genome. In this review, we compile an exhaustive list of the known human mutations and associated pathologies found in the mitochondrially-encoded cytochrome b gene as well as the fewer mutations in the nuclear genes coding for the complex III structural subunits and accessory proteins such as BCS1L involved in the assembly of the complex III. Due to the inherent difficulties of studying human biopsy material associated with complex III dysfunction, we also review the work that has been conducted to study the pathologies with the easy to handle eukaryotic microorganism, the yeast Saccharomyces cerevisiae. Phenotypes, biochemical data and possible effects due to the mutations are also discussed in the context of the known three-dimensional structure of the eukaryotic complex III. This article is part of a Special Issue entitled: Respiratory complex III and related bc complexes.