A patient with Leber's hereditary optic neuropathy (LHON) is found to have mitochondrial DNA mutation at position m.11778G>A. Regarding inheritance and genetic counseling, which statement is CORRECT?
- A It is X-linked recessive and affects only males
- B Mitochondrial DNA is inherited exclusively from the mother; all children of an affected mother will inherit the mutation, but penetrance is incomplete — males are affected more frequently than females ✓
- C Autosomal dominant inheritance with 50% risk to offspring
- D It is a de novo mutation not transmissible to offspring
Explanation
LHON is caused by point mutations in mitochondrial DNA (most commonly m.11778G>A, m.3460G>A, m.14484T>C), which is inherited exclusively via maternal transmission — all children of an affected or carrier mother will inherit the mutation. However, penetrance is incomplete (approximately 50% of males and 10% of females with the mutation develop visual loss), with males being four to five times more likely to develop visual loss than females, possibly due to X-linked modifier genes or hormonal factors. Understanding this counseling point distinguishes LHON from other optic neuropathies.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.