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case_images: Visual acuity fluctuations during first eight months since disease onset.
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case_images: At that point, the left eye (LE)'s visual acuity (VA) was 0.6 Snellen (0.22 LogMAR) (Figure 1). LE vision deteriorated again (Figure 1). LE VA fluctuated daily from 0.2 to 0.4 Snellen (0.7-0.4 LogMAR) and color vision was 3-9/11 Ishihara. Snellen (0 LogMAR); Ishihara 15/15). Soon after that, the patient noticed RE visual decline which in two weeks deteriorated to counting fingers (CF) or 0.0025 Snellen (2.6 LogMAR) (Figure 1) with an Ishihara of 0/15. MRI showed no signs of demyelination (Supplementary Figure S1). In two months (8 months since onset), it declined to VA: RLE CF (0.0025 Snellen; 2.6 LogMAR); Ishihara: RE 1/11, LE 2/11 (Figure 1).
case_images: Fundoscopy appearance of our patient. Note the hyperemic optic disks during first eight months since disease onset: only later did the optic disk pallor appear.
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case_images: He was treated for three days with methylprednisolone sodium succinate i.v. (1 g/day) and his VA in the LE worsened further to 0.2 (0.7 LogMAR) (Figure 2). Fundoscopy showed hyperemic optic disks (Figure 2). His optic disks were still pink (Figure 2) and he had central scotoma in the visual field (Figure 3). Optic disks were still pink/hyperemic (Figure 2), with large central scotomas in both visual fields (Figure 3). Microperimetry (Nidek MP1, fast strategy) showed improved fixation, and more stimuli were detected (Supplementary Figure S2).
case_images: Visual field scotomas with the disease progression (Goldmann:uppermost picture; Octopus G2TOP program:lower two pictures).
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case_images: His optic disks were still pink (Figure 2) and he had central scotoma in the visual field (Figure 3). Optic disks were still pink/hyperemic (Figure 2), with large central scotomas in both visual fields (Figure 3). The patient reached his nadir visual acuity of CF (0.0025 Snellen; 2.6 LogMAR) in 8 months; optic disks were pink/hyperemic the whole time (Figure 3). Optical coherence tomography showed no structural improvement, not even in the places where there was improvement in the microperimetry (Supplementary Figures S3 and S4).
case_images: Visual acuity and color vision changes during the follow-up period.
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case_images: Over the course of 5 years, VA reached 0.5 Snellen in the RE and 0.7 Snellen in the LE (0.3 and 0.15 LogMAR) (Figure 4). Optical coherence tomography showed no structural improvement, not even in the places where there was improvement in the microperimetry (Supplementary Figures S3 and S4).
case_images: Visual field changes over time (Octopus G2TOP) showing less dense centrocecal scotomas with islands of normal sensitivity and improvement of visual acuity.
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case_images: RNFL thickness around optic disks remained low, but there was a bilaterally relatively preserved inferior nasal sector (Supplementary Figure S5).
case_images: Shortening of the VEP peak time with visual acuity improvement.
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case_images: Mitochondrial respiration in the LHON patient's PBMCs is lower compared to a healthy control. Representative overlapped traces are presented, with different respiratory states: ROUTINE, LEAK, OXPHOS CI, OXPHOS CI+II, OXPHOS CII and ROX. Dig:digitonin; P:pyruvate; M:malate; G:glutamate; D:ADP; S:succinate; Rot:rotenone; Ama:antimycin A.
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case_images: PERG N95 and PERG P50 amplitude showed slight gradual amplitude increase with visual improvement (also probably due to better fixation) (Supplementary Figures S7 and S8). ROUTINE and OXPHOS CI respiratory states, which represent respiration of intact cells based on endogenous substrates and oxidative phosphorylation capacity with complex I-linked substrates (Figure 7). Respiration of the patient's PBMCs was slightly lower compared to the control in the OXPHOS CI+II state, which is consistent with a lower OXPHOS CI capacity, while no difference was observed in phosphorylation capacity with complex II-linked substrates (OXPHOS CII respiratory state) between the patient and control PBMCs.
case_images: The LHON patient's PBMCs produce more reactive oxygen species compared to those of the healthy control. Representative histograms from two independent experiments are shown. The ROS and superoxide production, determined by flow cytometry after DHR and DHE staining, respectively, was higher in the PBMCs collected from the patient with LHON compared to the healthy control in which the production was arbitrarily set to 1.
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case_images: PERG N95 and PERG P50 amplitude showed slight gradual amplitude increase with visual improvement (also probably due to better fixation) (Supplementary Figures S7 and S8).
case_images: Mitochondrial membrane of LHON patient's PBMCs is depolarized compared to the healthy control. Representative histograms from two independent experiments are shown. Mitochondrial membrane potential (DeltaPsim) of healthy control's PBMCs was arbitrary set to 1. LHON patient's PBMCs show an increase in mean fluorescence FL1/FL2 ratio, indicating depolarization.
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case_images: The same mitochondrial variant, but at different levels of heteroplasmy, has been confirmed in the patient's mother and both sisters: 38%, 47% and 23%, respectively (I-2, II-1, II-3; Supplementary Figure S9).
case_images: (A) Hydrophobicity analysis highlights a significant reduction in hydrophobicity at residues 188-191 in the mutated protein compared to the wild type. (B) The molecular surface representation reveals that the mutation alters the local chemical environment of the transmembrane region. The mutated residues are highlighted, showing a disruption in the uniform hydrophobic surface, with polar patches emerging due to the threonine substitution.
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case_images: AlphaFold2 to generate structures of both the wild type and protein with the p.I188T variant. A substitution of the hydrophobic isoleucine with the polar threonine at position 188 occurs within the transmembrane region of MT-CYB (Figure 10A). Kyte-Doolittle hydrophobicity analysis revealed a significant decrease in hydrophobicity at residues 188-191 in the mutated protein compared to the wild type (Figure 10A), suggesting destabilization of protein-lipid interactions crucial for membrane anchoring and structural integrity. Surface visualization further demonstrated the emergence of polar patches in the transmembrane region, disrupting the uniform hydrophobic surface and potentially interfering with protein folding and complex assembly (Figure 10B).