What are the other Names for this Condition? (Also known as/Synonyms)

• Chronic Progressive External Ophthalmoplegia (CPEO) and Myopathy
• Kearns-Sayre Mitochondrial Cytopathy
• Oculocraniosomatic Neuromuscular Disease with Ragged Red Fibers

What is Kearns-Sayre Syndrome? (Definition/Background Information)

• Kearns-Sayre Syndrome (KSS) is a rare disorder that particularly affects the eyes. It usually manifests before or around the time an individual reaches adulthood
• In this disorder, the affected individuals have impaired eye movement due to weak eye muscles. Apart from this, the signs and symptoms of Kearns-Sayre Syndrome may include abnormalities of the heart, walking difficulties, and loss of balance
• The cause of Kearns-Sayre Syndrome is due to deletion of mitochondrial DNA resulting in abnormally-functioning mitochondria. KSS does not run in families and cannot be inherited
• Kearns-Sayre Syndrome is an incurable condition and symptomatic and supportive treatment is provided. However, since it is a progressive disorder, the prognosis of KSS is generally poor

Who gets Kearns-Sayre Syndrome? (Age and Sex Distribution)

• Kearns-Sayre Syndrome is a rare disorder with an incidence rate of about 1 in 33,000-100,000 among the general population
• The condition typically develops by or before the age of 20 years in the affected individual
• Both male and female sexes are prone to the disorder
• There is no racial or ethnic predominance observed

What are the Risk Factors for Kearns-Sayre Syndrome? (Predisposing Factors)

• No risk factors have been identified for Kearns-Sayre Syndrome

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Kearns-Sayre Syndrome? (Etiology)

• The cause of Kearns-Sayre Syndrome is due to deletion of DNA that is specific to mitochondria development
• Mitochondria are the powerhouse of the cell and are responsible for energy production; this deletion results in abnormally-functioning mitochondria leading to the characteristic symptoms of KSS. The reason for this deletion is unknown
• Kearns-Sayre Syndrome develops due to mutation in certain genes, which take place after birth. However, since the germ cells (the cells responsible for development of sperms or ova) are not affected, it is called somatic mutation
• It is not inherited from one’s parents in most cases. And because it usually does not run in families, KSS occurs due to sporadic mutation
• However, in a minority, this disorder may be inherited from the mother (maternal inheritance)

Maternal inheritance: In the maternal type of inheritance, mutations usually occur in genes of the mitochondrial DNA. During the development of the fetus, the mitochondria develop in the cells using information from the egg cells. Only females pass on the mitochondrial DNA to the developing embryo. Hence, it is called a maternal inheritance. Both males and females can be affected. The inherited genetic defects to the mitochondrial DNA can cause disorders that can appear in every generation of the family. It is the females that pass the mutation to the next generation and not the males.

What are the Signs and Symptoms of Kearns-Sayre Syndrome?

The signs and symptoms of Kearns-Sayre Syndrome may include the following:

• Progressive weakening of the eye muscles affecting eye movement and causing ptosis (droopy eyelids)
• Weakening of the limb muscles
• Short stature
• Streaked retina due to breakdown of the retina, which may result in loss of vision
• Cardiac arrhythmias due to abnormal electrical signals affecting the heartbeat
• Loss of coordination and balance resulting in unsteady gait
• Cerebrospinal fluid (CSF) with high protein content
• Kidney defects

How is Kearns-Sayre Syndrome Diagnosed?

Diagnostic tests that are performed for Kearns-Sayre Syndrome may include:

• Complete physical examination with evaluation of comprehensive medical history
• Testing of blood and urine samples
• Lumbar puncture for CSF analysis
• MRI of brain
• ECG for detecting heart abnormalities
• Assessment of ears (audiometry) and eyes (electroretinography)
• Genetic testing to detect mutations in the mitochondrial DNA using molecular methods
• Muscle biopsy: A biopsy is performed and sent to a laboratory for a pathological examination, who examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Kearns-Sayre Syndrome?

Complications due to Kearns-Sayre Syndrome could include:

• Heart defects
• Totally impaired vision, due to severe paralysis of the eye muscles
• Hearing loss
• Dementia and decline of mental function
• Complications due to the effect of certain drugs (such as tetracycline, chloramphenicol, and valproic acid) on the mitochondria
• Diabetes mellitus, in rare cases

How is Kearns-Sayre Syndrome Treated?

Management of Kearns-Sayre Syndrome is undertaken on a case-by-case, symptomatic basis; the condition cannot be cured. The measures considered are supportive and dependent upon the health condition of the individual, acuity of the symptoms, etc. These include:

• Heart-related abnormalities are managed with the use of pacemaker implants, in order to avoid any heart block
• Esophageal-associated conditions and swallowing difficulties may require surgical treatment
• An ophthalmologist might be required to assist in eye-related defects
• For ear-related abnormalities, the use of cochlear implants and hearing aids may be beneficial
• Medications are used to treat endocrinological defects
• Physical therapy and exercises to strengthen weakened muscles - however, individuals with severe KSS may find this difficult
• Supplementation with Coenzyme Q10 (a vital enzyme required for proper cell functioning), and other vitamins may be beneficial for the heart, gums, and body immune system
• Regular check-up and screening is essential to evaluate progress of the condition

How can Kearns-Sayre Syndrome be Prevented?

• Kearns-Sayre Syndrome is a serious medical disorder caused by genetic and non-genetic factors in an individual; it cannot be prevented
• Avoid medications that adversely affect mitochondria, or its function; and the use of dental anesthetic, such as articaine
• If there is a family history of the condition, then genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• Also, in such cases, genetic counseling will help assess risks, before planning for a child

What is the Prognosis of Kearns-Sayre Syndrome? (Outcomes/Resolutions)

• Current medical and healthcare advances have had limited success in treating Kearns-Sayre Syndrome. The general outcome of the disorder is not positive, for most individuals do not live past the age of 40 years
• KSS is a neuromuscular disorder where multiple organs are affected and the fatalities are mainly due to heart-related complications
• Symptomatic treatment can help manage the condition to a certain extent and provide a measure of comfort to the individuals

Additional and Relevant Useful Information for Kearns-Sayre Syndrome:

There are voluntary organizations and support groups that provide help and understanding to the families and parents of the Kearns-Sayre Syndrome affected.