Definition

LHON arises from one of three common ('primary') point mutations (m.11778G>A, m.3460G>A, m.14484T>C) in the mitochondrial DNA genes MT-ND1, MT-ND4, and MT-ND6, which encode Complex I subunits of the electron transport chain. The resulting impairment of oxidative phosphorylation leaves retinal ganglion cells unable to meet their energy needs, causing painless, rapidly progressive bilateral central vision loss between ages 15 and 35; penetrance is markedly higher in men (~50% vs 10% in women).

Gene/region examined

mtDNA - A52T, mtDNA - R340H, mtDNA - M64V

Method

Sequence analysis

Accepted sample types

EDTA blood, AF, CVS

Inheritance

Inherited, mitochondrial (maternal) inheritance, with variable penetrance and heteroplasmy.

Related Tests

Inheritance Patterns

Describes how a genetic condition is passed on within a family. There are five main patterns

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Carrier (Heterozygous / Homozygous)

Why it matters: In autosomal recessive inheritance, when each parent is a carrier (while both appear healthy), the chance of their child being born with the disease is 25% in each

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VUS (Variant of Uncertain Significance)

This is the situation where the test has detected a change in the DNA, but the role of this change in the development of disease is unconfirmed.

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How to Read a Genetic Test Result (Positive / Negative / VUS)

A genetic test result falls into three main categories

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Types of Genetic Tests

A genetic test is a type of medical test that detects changes in genes, chromosomes or proteins. Today there are more than 77,000 genetic tests available.

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