Kearns Sayre Syndrome

What else is it called?

  • Chronic progressive external ophthalmoplegia and myopathy 
  • Chronic progressive external ophthalmoplegia with ragged red fibres 
  • CPEO with myopathy 
  • CPEO with ragged red fibres 
  • KSS 
  • Mitochondrial cytopathy 
  • Occulocraniosomatic syndrome (obsolete) 
  • Ophthalmoplegia, pigmentary degeneration of the retina and cardiomyopathy 
  • Ophthalmoplegia plus syndrome 

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What causes it?

This disorder affects your mitochondria, which release energy into your cells. Your body is made up of different cells that each have their own specific roles. These cells need energy so that they can carry out their functions in the body. 

With Kearns Sayre syndrome, a significant amount of the genetic material in the mitochondria DNA (mtDNA) has been deleted. Therefore, your cells cannot get the energy needed to function as normal. Affected muscles and organs cannot carry out their roles properly and you may develop complications that are likely to get progressively worse over time. 

How common is it?

KSS has been reported in anywhere between 1 and 9 in every 100,000 people, although the exact numbers are not known. Males and females are equally likely to be affected, and race and ethnicity do not seem to have any effect on the likelihood of being diagnosed with KSS. 

What are the signs and symptoms?

Symptoms usually appear before 20 years old. They are progressive, so they will become more prominent as time goes on. It is important to get any potential symptoms checked as soon as possible by your medical team. 

There are three main symptoms that are typical of KSS. These are: 

  • Progressive paralysis of your eye muscles, which may look like drooping eyelids (ptosis) or inability to move your eyes. People with this symptom are more likely to move their head and neck to see, instead of their eyes. 
  • An accumulation of pigment on your eyes, which normally looks like spots in your vision. 
  • Heart disease, blockages, or abnormalities. 

You may also be affected by a number of other symptoms that are common in people with KSS: 

  • Problems with coordination and balance (ataxia) 
  • Developmental delays 
  • Short in height (dwarfism) 
  • Hearing loss or deafness 
  • Loss of vision 
  • Memory loss 

Life expectancy depends on the organs that are affected. However, with proper support and treatment, many people live a long life.

How is it diagnosed?

To diagnose KSS, medical professionals will look for the three main symptoms of the disorder and whether they have begun before you reach 20 years old. A molecular genetic test will confirm the diagnosis. 

Specialised tests such as an electrocardiogram (sensors attached to your skin to monitor your heart), muscle biopsy (a sample of tissue taken from your muscle), and a lumbar puncture (a needle in your back to take fluid from your spinal cord, also known as a spinal tap) are used to check the seriousness of the symptoms. 

KSS may be diagnosed as another disease that involves large mtDNA deletions. It may also be mistaken for Pearson syndrome, or maternally-inherited progressive external ophthalmoplegia. 

This disorder is not currently detected as part of the newborn screening process in the UK or in other countries. 

Can it be treated?

Treatment is available to help you to manage the syndrome, however there is no cure for KSS.  

Your medical team may recommend inserting things such as a pacemaker or other instrument to help with any heart issues. You may also need hearing aids or eye surgery. This will be dependent on how KSS affects you. For more information, speak to your medical team. 

Although KSS is not curable, it is manageable with guidance and medical intervention. Most people with the disorder can expect a typical life expectancy, but this is dependent on the severity of your symptoms and the organs that are affected. 

Do my family need to be tested?

KSS is very rarely inherited from parents. There is only a 4% chance of a mother passing KSS to her child.   

The disorder is typically caused by a mutation of your mitochondrial DNA, which means it is sporadic (happens for no apparent reason). It is unlikely that anybody else in your family will also have KSS.

Relevant Organisations


References are available on request. Please contact Helen Morris by phoning 0845 241 2173 or emailing [Resource Library No: AAP002]. 

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