Kearns-Sayre syndrome is a rare condition caused by changes to mitochondrial DNA. Its symptoms affect the eye as well as other areas of the body.

Kearns-Sayre syndrome (KSS) is a rare neuromuscular disorder that is caused by abnormalities in mitochondria. Mitochondria are small structures in cells that produce the energy needed for your cells to function.

KSS is rare. Researchers estimate that it affects about 1 in 100,000 people.

KSS is a type of mitochondrial encephalomyopathy, meaning that it can cause a variety of problems with muscles and the nervous system. The symptoms of KSS affect the eyes as well as other parts of the body.

Your mitochondria contain a small amount of their own DNA. This is called mitochondrial DNA.

KSS is caused by changes to your mitochondrial DNA. About 90% of KSS cases happen due to random deletions in mitochondrial DNA.

These deletions can vary in size. However, the most common one involves the deletion of almost 5,000 base pairs and accounts for about one-third of all KSS diagnoses.

You inherit your mitochondrial DNA from your mother. As such, in very rare cases, you may also inherit KSS.

The symptoms of KSS typically come on before the age of 20. There are three primary findings in people with KSS. These symptomatic findings include:

Chronic progressive external ophthalmoplegia (CPEO)

CPEO is a progressive weakening of eye muscles. Progressive means that the condition gets worse as time passes.

CPEO may first appear as a drooping eyelid. Over time, people with KSS may need to use their forehead muscles to help raise their eyelids or may lift their chin in order to see better.

Weakening of the eye muscles can make it difficult to move the eyes. Due to this, people with KSS may turn their heads in order to see objects located in the periphery of their vision.

It’s possible for CPEO to be associated with muscle weakness in other parts of the body as well, such as the face, throat, and limbs. This can lead to symptoms like:

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Progression of Kearns-Sayre Syndrome. Photography courtesy of Sebastiá, et al., Dove Medical Press Limited.

Pigmentary retinopathy

People with KSS have a buildup of pigmented material in the tissues lining the eye, giving it a “salt-and-pepper” appearance. This can lead to damage of the retina, the part of your eye that converts light into nerve signals that your brain can process.

The effects of pigmentary retinopathy can lead to a variety of vision problems, including:

Heart block

People with KSS develop problems with the electrical impulses that control the activity of the heart muscle. You may see this referred to as heart block. This can lead to:

Other symptoms of Kearns-Sayre syndrome

In addition to what’s discussed above, people with KSS may also have other signs and symptoms as well. These include:

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The symptoms of KSS can resemble those of other health conditions, particularly other mitochondrial disorders. KSS can be suspected when the three primary findings discussed above are present and symptom onset is by age 20.

The first part of the diagnostic process involves your doctor getting a thorough medical history and doing a physical and eye exam. They’ll then order tests to help rule out other conditions and confirm the diagnosis.

Some of the tests that may be done are:

KSS is associated with a variety of complications. These can include:

  • increasing trouble with eye or other muscle movement
  • vision loss
  • hearing loss
  • dementia

Heart block in people with KSS is also an important cause of complications, particularly sudden cardiac arrest. It’s estimated that heart block can cause death in 20% of people with KSS.

There’s no cure for KSS. Additionally, because KSS is progressive, its symptoms will continue to worsen as time passes. Treatment for KSS is targeted at managing symptoms, preventing complications, and boosting quality of life.

Typically, a variety of different healthcare professionals are involved in treating KSS. These can include, but aren’t limited to:

Some of the potential treatments for KSS include:

The outlook for KSS can depend on the severity of symptoms and the specific parts of the body impacted. Generally speaking, early diagnosis and treatment can help to improve outlook.

KSS is a condition that affects cellular mitochondria. It’s typically caused by spontaneous deletions of mitochondrial DNA, but can occasionally be inherited.

The key findings in KSS include progressive weakening of the eye muscles, pigmentary retinopathy, and heart block. Other signs and symptoms may be present as well.

KSS is a progressive condition for which there’s no cure at this time. Treatment aims to manage symptoms, prevent complications, and improve quality of life. The outlook for KSS depends on its severity and the parts of the body affected.