Kearns-Sayre Syndrome: Navigating a Rare Mitochondrial Disorder
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 17, 2026
Quick Answer: Key Facts About Kearns-Sayre Syndrome
Kearns-Sayre syndrome is a rare mitochondrial neuromuscular disease caused by a defect, often a large deletion, in mitochondrial DNA, usually beginning before age 20. Core features include drooping eyelids, weak eye muscles and retinal changes, plus heart conduction defects or ataxia. It is diagnosed with genetic testing and muscle biopsy. There is no cure, but supportive care helps.
Feature | Details |
Condition type | A rare mitochondrial neuromuscular disease. [1] |
Primary cause | |
Typical onset | |
Core features | Drooping eyelids and weak eye muscles (CPEO), pigmentary retinopathy, plus at least one of heart conduction defects, ataxia or high protein in the spinal fluid. [3] |
How common | |
Diagnosis | |
Treatment |
What the research says
Heart conduction problems progress and may call for early pacing. In a prospective study of 15 young people with KSS (mean age 16.6 years), every participant had at least one intraventricular conduction defect, and in 6 it progressed to atrioventricular block. Pacemakers were implanted in 11 patients, and four patients died at a mean age of 14.7 years, none of them suddenly. The authors suggest that a pacemaker may be indicated from the first appearance of a bi-fascicular block, which a standard ECG can detect. (Di Mambro et al., Europace, 2021) [4]
Droopy eyelids are often the first sign, and many organs can be involved. In a UK cohort of 34 children with single large-scale mtDNA deletion disease, the most common first sign was isolated ptosis (16 of 34; 47%), and ten children were classified as having KSS. Kidney tubular or glomerular dysfunction was documented in 17 of 20 (85%) children who had detailed investigations. The deletion was found in blood and/or urine cells in every case tested, so a muscle biopsy was not necessary for diagnosis in this age group. (Broomfield et al., J Inherit Metab Dis, 2015) [5]
The clinical picture changes over time. A retrospective natural-history study of 30 people with single large-scale mtDNA deletion syndromes found that the clinical presentation tends to evolve over time. Higher blood heteroplasmy (a larger share of abnormal mtDNA) was linked to an earlier age of onset, growth differentiation factor 15 was elevated in all participants, and fatigue increased and quality of life decreased with advancing age. (Ganetzky et al., Genet Med, 2025) [6]
What Is Kearns-Sayre Syndrome?
Kearns-Sayre syndrome (KSS) is a rare, progressive neuromuscular condition that stems from a defect in the DNA of the mitochondria. Mitochondria are tiny rod-like structures found in every cell of your body except red blood cells, and they are often called the “energy factories” of the body because they produce 90% of the energy needed to support body function and growth. When they are damaged, the body does not get enough energy to work properly, and muscle and nerve cells, which depend on a lot of energy, are often affected first. [1]
KSS is named after Thomas P. Kearns and George Pomeroy Sayre, who first described the disease in 1958. Symptoms typically appear before a person reaches age 20, and because the condition affects several organ systems at once, it requires a coordinated medical approach. [1] It affects males and females in equal numbers. [2]
What role does mitochondrial DNA play in Kearns-Sayre syndrome?
KSS happens because of a genetic mutation in mitochondrial DNA (mtDNA), the DNA that carries the genes needed for healthy mitochondrial function. [1] NORD explains that most cases appear to result from a new (de novo) deletion of a large amount, typically about 25%, of the mtDNA, and that genetic testing shows missing mtDNA in about 80% of people with KSS. [2] The genetic change usually happens as a baby develops during pregnancy, although the condition can occasionally be passed down from the mother. [1]
Energy production: mitochondria that are damaged cannot make enough energy, so cells can be damaged or die. [1] [3]
Systemic failure: tissues with high energy needs, such as nerves and muscles, are often damaged first. [1]
Progressive nature: symptoms typically worsen over time. [1]
Inheritance: mtDNA comes from the mother's egg cell, so an affected mother can pass a mitochondrial variant to her children, but most cases of KSS occur without any family history. [2] [3]
Normal and altered mtDNA can exist side by side in the same cell, which is called heteroplasmy. The mix can differ from tissue to tissue, which can lead to different symptoms and different levels of severity, even among members of the same family. The deletion might not be found in a blood or cheek swab sample but can be found in a muscle biopsy. [2] There is no way to prevent KSS, and nothing a parent does causes it. [1]
What are the early symptoms and signs of Kearns-Sayre syndrome?
Signs of KSS usually occur before age 20 and first affect the eyes. Over time, the disease may cause blindness. Early symptoms include: [1]
Ptosis: drooping of one or both eyelids.
Pigmentary retinopathy: damage to the light-sensitive tissue of the retina, which causes difficulty seeing, especially in the dark.
CPEO: chronic progressive external ophthalmoplegia, which means weak or paralyzed eye muscles.
KSS also causes a range of other symptoms, including hearing loss, impaired thinking or dementia, heart defects caused by blocked electrical signals (cardiac conduction defects), hormone abnormalities including diabetes, excess protein in the spinal fluid, kidney problems, lack of coordination (ataxia) and balance problems, weakness in the arms or legs, and short stature. Seizures are rare. [1]
How is Kearns-Sayre syndrome diagnosed?
KSS can be challenging to diagnose because it can involve many body systems and its symptoms overlap with other conditions. Providers review your medical history and symptoms, perform a physical exam and may order additional tests. [1] The diagnosis rests on a few characteristic features: weak eye muscles with drooping eyelids, pigmentary retinopathy, and at least one of heart conduction defects, ataxia or high protein in the spinal fluid. [3]
Muscle biopsy: a sample of muscle tissue is examined for ragged-red fibers, which indicate abnormal muscle cells due to mitochondrial disease. The biopsy can also show the deleted mtDNA, which may not be detected in a blood sample. [1] [2]
Genetic testing: a blood test that looks for gene changes, often alongside genetic counseling. [1] [2]
Electroretinogram (ERG): a retinal exam that assesses how well the retina is working. [1]
Spinal tap: checks the spinal fluid for excess protein (above 100 mg/dL) or low folate. [2]
Electrocardiogram (ECG): detects the presence and severity of heart block. [2]
Other tests: eye and hearing exams, urine and blood tests and, in some cases, imaging such as CT, MRI or EEG to rule out other conditions. [1]
In children, one UK study found the mtDNA deletion in blood and/or urine cells in every case tested, so a muscle biopsy was not necessary for diagnosis in that age group. [5] Early detection is essential for effective treatment. [1]
How is Kearns-Sayre syndrome managed and treated?
Kearns-Sayre syndrome has no cure, so treatment instead focuses on managing symptoms and reducing complications. Treatment focuses on managing symptoms and reducing complications as the condition progresses, and it is personalized to the organ systems involved. [1] [2] Because KSS affects so many parts of the body, the care team may include an eye specialist, a hearing specialist (audiologist), a cardiologist, an endocrinologist, a geneticist, a neurologist, and physical and occupational therapists. [1]
Cardiac pacemaker: People with KSS are at risk of complete heart block, which can lead to a dangerously slow heart rate or sudden cardiac arrest. Doctors may recommend a preventive (prophylactic) pacemaker, and regular check-ups with a cardiologist are essential. [2]
Eye care: Eyelid surgery (blepharoplasty) or an eyelid sling can help keep the eyes open and improve vision. Whether surgery helps retinal problems depends on how advanced they are, and vision aids may help people with vision loss. [1] [2]
Hearing support: A hearing aid or a cochlear implant may be recommended for hearing loss. [1] [2]
Therapy: Physical and occupational therapy can help with coordination, strength and balance problems. [1]
Supplements: Folic acid (or folinic acid) may be recommended to address low folate in the spinal fluid. Coenzyme Q10 is still being studied, although some doctors suggest it. [1] [2]
Hormone care: Insulin treats diabetes, and hormone replacement can treat other endocrine abnormalities. [1] [2]
Ongoing monitoring is necessary because new symptoms often arise as organ systems are affected over time. [1]
What is the outlook and long-term care for Kearns-Sayre syndrome?
The outlook for KSS depends on the symptoms and their severity. Most people with the condition live for several decades, and supportive treatment can provide a longer, healthier life. [1] Regular check-ups are essential so that heart and hormone problems can be caught before they become emergencies. [2]
Genetic counseling is recommended, and mitochondrial disease organizations such as the United Mitochondrial Disease Foundation (UMDF) and MitoAction can connect patients and families with others facing similar challenges. [2] [7] [8] Research continues, including experimental genetic therapies and Coenzyme Q10, but these treatments are still being studied. [2]
Learn more. For more evidence-based health guides, visit Rinnit.com.
Frequently Asked Questions
Is Kearns-Sayre syndrome a form of muscular dystrophy?
No. KSS is a mitochondrial disease caused by a defect in mitochondrial DNA. It does cause muscle weakness, but it is not a muscular dystrophy. [3]
Can I prevent KSS in my children?
There is no way to prevent KSS, and nothing a parent does causes it. Because it is a genetic disorder, genetic counseling is recommended for families. [1] [2]
Why does it affect the eyes first?
Muscle and nerve cells depend on a lot of energy, so they are often damaged first in mitochondrial disease, and in KSS the first signs usually involve the eyes. [1]
Is a pacemaker always necessary?
Not for everyone, but people with KSS are at risk of complete heart block, which can cause a dangerously slow heart rate or sudden cardiac arrest. Doctors may recommend a preventive (prophylactic) pacemaker, and regular check-ups with a cardiologist are essential. [2] [4]
Can adults develop KSS?
Symptoms usually appear before age 20, but they may appear during infancy or adulthood. [2]
Does it affect intelligence?
Some people develop impaired cognition (difficulty thinking) or dementia as the disease progresses, but this varies from person to person. [1] [2]
What are ragged-red fibers?
Ragged-red fibers are abnormal muscle cells seen on a muscle biopsy that indicate mitochondrial disease. They contain an excess of mitochondria. [1] [3]
Is KSS the same as Leigh syndrome?
No. Both are mitochondrial disorders, but Leigh syndrome usually begins between 3 months and 2 years of age with progressive neurological deterioration, while KSS typically begins before age 20 with eye problems. [2]
Can physical therapy help with muscle weakness?
Physical and occupational therapy can help with coordination, strength and balance problems and can improve quality of life. [1] [2]
Why is folic acid prescribed?
Some people with KSS have low folate in the fluid around the brain and spinal cord (cerebral folate). Folic acid or folinic acid may be recommended to address this. [1] [2]
Are there supplements or new treatments being studied?
Coenzyme Q10, an antioxidant supplement, is being studied, and some doctors suggest it. Experimental genetic therapies that aim to reduce the number of damaged mitochondria are also being explored. [2]
How rare is this condition?
Can surgery fix drooping eyelids?
Eyelid surgery (blepharoplasty) or an eyelid sling can lift the eyelids to help keep the eyes open and improve vision. Whether surgery helps retinal problems depends on how advanced the changes are. [1] [2]
What is maternal inheritance?
Mitochondria come from the mother's egg cell, so an affected mother can pass a mitochondrial variant to her children, while a father cannot. Most cases of KSS, however, are new changes that happen without a family history. [2] [3]
What is the life expectancy with KSS?
It depends on the symptoms and their severity. Most people with KSS live for several decades, and supportive treatment can provide a longer, healthier life. [1]
Conclusion
Kearns-Sayre syndrome is a complex disorder that shows how important mitochondria are to human health. It presents real challenges, but supportive care, careful monitoring of the heart and other organs, and a coordinated team of specialists can help people live longer and healthier lives. Early detection and a dedicated medical team remain the most important factors in navigating this rare mitochondrial condition. [1] [2]
Related Reading
Understanding MELAS Syndrome: Causes, Symptoms, and Management explains another mitochondrial disorder that affects the brain and muscles.
Understanding Leigh Syndrome: A Comprehensive Guide to Mitochondrial Health explains a mitochondrial disease that usually starts in early childhood.
Heart Block: Understanding Types, Symptoms, and Treatment explains the heart signal problem that can develop in Kearns-Sayre syndrome.
Droopy Eyelid Guide: Identifying and Managing Ptosis Symptoms explains drooping eyelids, an early sign of Kearns-Sayre syndrome.
References
Cleveland Clinic. Kearns-Sayre Syndrome. Cleveland Clinic. Last updated May 19, 2022. https://my.clevelandclinic.org/health/diseases/23036-kearns-sayre-syndrome
National Organization for Rare Disorders (NORD). Kearns-Sayre Syndrome. NORD. Last updated March 18, 2025. https://rarediseases.org/rare-diseases/kearns-sayre-syndrome/
Genetic and Rare Diseases Information Center (GARD). Kearns-Sayre syndrome. GARD. Last updated September 2026. https://rarediseases.info.nih.gov/diseases/6817/kearns-sayre-syndrome
Di Mambro C, Tamborrino PP, Silvetti MS, et al. Progressive involvement of cardiac conduction system in paediatric patients with Kearns-Sayre syndrome: how to predict occurrence of complete heart block and sudden cardiac death? Europace. 2021;23(6):948-957. PMID 33336258. https://doi.org/10.1093/europace/euaa335
Broomfield A, Sweeney MG, Woodward CE, et al. Paediatric single mitochondrial DNA deletion disorders: an overlapping spectrum of disease. J Inherit Metab Dis. 2015;38(3):445-57. PMID 25352051. https://doi.org/10.1007/s10545-014-9778-4
Ganetzky R, Stanley KD, MacMullen LE, et al. Recognizing the evolution of clinical syndrome spectrum progression in individuals with single large-scale mitochondrial DNA deletion syndromes (SLSMDS). Genet Med. 2025;27(5):101386. PMID 39985363. https://doi.org/10.1016/j.gim.2025.101386
United Mitochondrial Disease Foundation. Home page. United Mitochondrial Disease Foundation. Accessed October 30, 2026. https://umdf.org/
MitoAction. Home page. MitoAction. Accessed October 30, 2026. https://www.mitoaction.org/
Medical disclaimer
This article is for general educational purposes only and is not a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
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