Can LHON Mothers Pass It On—and Will Children Have Symptoms?

Yes, if you are a woman carrying a Leber hereditary optic neuropathy (LHON) pathogenic variant (often called a “mutation”), you can pass it to your children. However, passing on the genetic variant does not mean your children will inevitably lose their vision. Because of a phenomenon called incomplete penetrance, a child can inherit the variant and never experience symptoms.

What This Means for Each Child

Every child inherits their mitochondria (the energy-producing centers of cells) exclusively from their mother ^[1]. How this affects your children depends on two key concepts:

• The amount of the variant inherited: If all of your mitochondrial DNA carries the LHON variant (a state called homoplasmy), you will generally pass the variant to all of your children. If you have a mixture of normal and variant mitochondrial DNA (called heteroplasmy), the amount of the variant passed to each child can vary, and some children may not inherit a detectable level of the variant at all ^[2][3].
• Inheriting the variant does not guarantee symptoms: Even if a child inherits a high level of the variant, they may remain perfectly healthy and asymptomatic throughout their life ^[4].

Who is Most Likely to Develop Symptoms?

The chance of developing vision loss from LHON is strongly influenced by sex. Males are significantly more likely to develop symptoms than females ^[4].

Broad lifetime estimates suggest that roughly 50% of male carriers and about 10% of female carriers will eventually experience vision loss ^[5]. However, these are approximate population-level figures. They cannot predict whether or when one particular child will develop symptoms. An individual’s true risk depends on the exact LHON variant, their broader genetic background, their age, and their family history ^[5][6].

The exact reason for this sex difference is still under investigation. One proposed explanation is that the female hormone estrogen might help boost mitochondrial function, potentially partially compensating for the genetic defect ^[7]. Please note that this is a research hypothesis, and hormone therapy is not an established or recommended treatment to prevent LHON symptoms ^[8].

Factors Associated with Risk: What You Can Do

While you cannot control the genes your children inherit, there are environmental exposures associated with a higher risk of an LHON carrier developing symptoms. Because LHON stresses the mitochondria, doctors recommend avoiding toxins that further impair mitochondrial function. However, it is important to understand that while avoiding these triggers is a prudent way to reduce risk, it cannot absolutely guarantee that symptoms will not develop, and no one should ever feel they caused their own or their child’s vision loss.

• Smoking: Tobacco smoke is one of the most widely recognized modifiable risk factors ^[9][10]. Research indicates that smoking further reduces the energy output of cells carrying LHON variants. It is strongly recommended that carriers avoid smoking and secondhand smoke ^[10].
• Alcohol: Heavy alcohol consumption has also been associated with an increased risk of developing symptoms in some studies ^[11][12]. While the evidence is less definitive than for smoking, many specialists advise limiting alcohol intake, though there is no clearly established “safe” threshold ^[12][6].
• Medications: Certain medications and eye-drop preservatives (like benzalkonium chloride) can theoretically stress the mitochondria ^[13][14]. However, you should never stop or change prescribed medications without consulting your doctor ^[15]. Always inform your prescribing clinicians that your child is an LHON carrier so they can weigh the proven benefits of a medication against any potential mitochondrial risks ^[15].

If a Child Notices Vision Changes

Because the onset of LHON can be unpredictable, it is important to know what symptoms to watch for.

• Early signs: LHON typically causes new, painless blurring or loss of central vision, a noticeable blind spot in the center of the visual field, or difficulty reading and recognizing colors (especially red and green) ^[16][17]. In children, the onset may sometimes be slower or more subtle ^[18].
• What to do: Symptoms commonly start in one eye, and the second eye is usually affected within weeks to a few months ^[16]. If your child experiences any new, unexplained visual symptoms, do not wait for a routine exam—seek prompt evaluation from an ophthalmologist or a neuro-ophthalmologist ^[19][20]. Early evaluation can help establish a baseline, connect you with low-vision support, and allow for discussions about potential treatments or clinical trials.

Deciding on Genetic Testing

Deciding whether to test asymptomatic children for the LHON variant is a complex and highly personal choice. A positive test can confirm that the variant is present, but it cannot predict if or when symptoms will occur ^[21].

Because there is no guaranteed preventative treatment, testing asymptomatic minors raises important questions about privacy, potential psychological distress, and future implications ^[21][22]. These decisions should be made with a genetic counselor or a clinician familiar with mitochondrial diseases. A counselor can provide emotional support, help you navigate family discussions, and, if you are planning future pregnancies, discuss preconception options based on your personal values and geographic location ^[10].