Kearns-Sayre syndrome (KSS)

Kearns-Sayre Syndrome (also known as KSS or Kearns-Sayre disease) is a rare genetic mitochondrial disease first described by doctors Kearns and Sayre in the 1950s. It’s caused by a spelling change (deletion) in mitochondrial DNA, which affects the body’s ability to produce energy.

What is Kearns-Sayre syndrome?

Kearns-Sayre syndrome is a primary mitochondrial myopathy that affects multiple parts of the body. It’s caused by deletions or mutations in mitochondrial DNA, which impair the ability of mitochondria – the cell’s energy producers – to function properly. Because mitochondria supply energy to almost every cell, KSS can have widespread effects, particularly in organs and tissues that require a lot of energy.

The word ‘syndrome’ means a pattern of symptoms, and the classic symptoms of KSS are weakness of muscles that move the eyes (known as chronic progressive external ophthalmoplegia or CPEO), droopy eyelids (known as ptosis) and changes in the cells that sense light at the back of the eye (retinopathy).

It’s also common to have heart rhythm problems, however Kearns-Sayre disease can affect other parts of the body too. It generally starts in childhood or early adulthood.

What are the symptoms of Kearns-Sayre disease?

Kearns-Sayre syndrome affects multiple parts of the body, often starting before the age of 20. Symptoms vary between individuals but commonly include:

Eyes

• Droopy eyelids (ptosis) sometimes needing surgery.
• Difficulty seeing in the dark (retinopathy).
• Reduced eye movement causing double vision and potentially causing worsened unsteadiness when walking.

Heart

• Abnormal heart rhythms (arrhythmias).
• Possible heart muscle changes – patients should have annual heart checks to identify such changes as early as possible.

Muscles

• Weakness of the muscles, especially in the shoulders, arms, hips and thighs.
• Respiratory muscle weakness, often requiring lung monitoring.

Brain & nervous system

• Poor balance or tremors.
• Learning difficulties or memory problems.

Swallowing & digestion

• Difficulty swallowing; risk of chest infections due to increased choking risk.

Endocrine & hormones

• Diabetes
• Low growth hormone, adrenal or parathyroid (calcium hormone) issues.

Kidneys

• Reduced kidney function, sometimes requiring monitoring.

What causes Kearns-Sayre syndrome?

KSS is caused by a deletion in mitochondrial DNA, inherited only from the mother. Mutations are usually sporadic, not passed from parent to child, and the severity of the disease varies depending on the proportion of affected mitochondria in different tissues.

How do you get a diagnosis of Kearns-Sayre syndrome?

Diagnosis typically involves:

• Clinical examination of symptoms (eyes, heart, muscles).
• Genetic testing for mitochondrial DNA deletions.
• Tissue analysis (blood, urine, muscle biopsy).

Are there any treatments for KSS?

Currently, as with all forms of mitochondrial disease, there is no cure for Kearns-Sayre syndrome, and current treatment focuses on managing symptoms:

• Eye surgery for droopy eyelids.
• Cardiac monitoring and pacemakers for heart rhythm problems.
• Physical therapy for muscle weakness.
• Endocrine treatment for hormone or diabetes issues.

Is there any ongoing research into Kearns-Sayre disease?

There is active research happening around the world into Kearns-Sayre syndrome, although because the condition is so rare, most studies look at KSS as part of a wider group of mitochondrial DNA deletion disorders.

In the UK, patients are supported through the NHS Rare Mitochondrial Disorders Service in London, Newcastle and Oxford, which also links into international research efforts. UK patients can often join large registries and global natural-history studies that include people with KSS and help scientists understand how the condition develops over time and what future treatments might target.

Research teams internationally continue to study mtDNA deletion syndromes to improve diagnosis, track progression and prepare for future clinical trials. Although there is no cure yet, this research is steadily building the foundations for new therapies, and families can usually get involved by speaking to their local mitochondrial specialist centre or by joining an international registry.

What support is available for Kearns-Sayre patients?

The NHS Highly Specialised Services for Mitochondrial Disorders provide expert care, including diagnosis, management of symptoms and ongoing monitoring. Genetic counselling is also available through NHS services to help families understand inheritance patterns and inform any future family planning.

The Lily Foundation are here to offer practical advice and emotional support to all patients and family members affected by a diagnosis of KSS, from in-person support weekends and information days to online meet-ups and private Facebook groups.

If you or someone you love is dealing with a diagnosis of a primary mitochondrial myopathy such as Kearns-Sayre syndrome, please take a look at our mitochondrial disease Q & A page which should help answer some of the questions you have. Please don’t hesitate to get in touch should you have further questions or would like to talk to someone about mitochondrial disease.