Mitochondrial Mutations in Ethambutol-Induced Optic Neuropathy

Area of Science:

• Ophthalmology
• Genetics
• Pharmacology

Background:

• Ethambutol-induced optic neuropathy (EON) is a known side effect of ethambutol, a tuberculosis drug.
• Mitochondrial dysfunction is implicated in various optic neuropathies.
• The role of specific mitochondrial mutations in EON pathogenesis remains unclear.

Purpose of the Study:

• To investigate the prevalence of OPA1 and Leber's hereditary optic neuropathy (LHON)-mitochondrial DNA (mtDNA) mutations in patients with EON.
• To determine the clinical impact of these mitochondrial mutations on EON patients.

Main Methods:

• Clinical evaluation of 47 EON patients, including visual acuity and fundus examination.
• Molecular screening for OPA1 gene mutations and LHON-mtDNA mutations using PCR-based sequencing.
• Targeted exome sequencing for comprehensive mutation detection.

Main Results:

• 15 OPA1 mutations in 18 patients and 2 LHON-mtDNA mutations in 4 patients were identified (46.8% detection rate).
• Patients with mitochondrial mutations presented younger (27.5 vs. 48 years) and showed more optic disc hyperemia (70.5% vs. 48%).
• Mitochondrial mutations and optic disc pallor were associated with a poorer vision prognosis.

Conclusions:

• OPA1 mutations may increase susceptibility to ethambutol toxicity, leading to EON.
• Mitochondrial genetic factors play a significant role in the development and clinical course of EON.
• Further research into genetic predispositions for EON is warranted.