Objective: The primary aim of this study was to describe clinical features of Chinese sporadic Leber hereditary optic neuropathy (LHON) caused by rare primary mitochondrial DNA (mtDNA) mutations.
Methods: We characterized a Chinese patient cohort with rare primary mtDNA mutations at Beijing Tongren Hospital between 2015 and 2018. The clinical features of these patients were retrospectively recorded and analyzed.
Results: Sixteen patients with LHON who had the selected rare primary mutations, including m.4171C>A (3 patients), m.10197G>A (1 patient), m.14459G>A (4 patients), and m.14502T>C (8 patients), were evaluated. The mean age at disease onset was 15 ± 6 years, and the male to female ratio was 15:1. Of 32 eyes of all patients, 75% (24/32) had a worst Snellen best-corrected visual acuity ≤0.1 (worse than 20/200), while 67% (2/3) who were carrying the m.4171C>A mutation experienced significant visual improvement. In addition, 40% (2/5) of patients with LHON carrying only m.14502T>C mutation had only mild visual impairment. Isolated manifestations of LHON was present in 94% (15/16) of all patients; 1 patient with the m.14459G>A mutation had LHON plus dystonia. Brain MRI T2 short tau inversion recovery sequences demonstrated optic atrophy in 62.5% (10/16); increased T2 signal in the optic nerve was found in 38% (6/16) of patients. The patient with LHON plus dystonia demonstrated optic atrophy and increased T2 signal in basal ganglia.
Conclusion: Patients with LHON and rare primary mutations have diverse clinical phenotypes. Those with the m.4171C>A mutation are more likely to have a good visual prognosis, while the m.14502T>C mutation may play a synergistic role in disease onset. Increased signal in the optic nerve on MRI is not rare, and this feature should not exclude LHON as the potential cause for optic neuropathy.