Kearns-Sayre syndrome (KSS) is a rare neuromuscular disorder with onset usually before the age of 20. It is caused by abnormalities in mitochondria—small rod-like structures found in every cell of the body that produce the energy that drives cellular functions.

KSS is characterized by progressive limitation of eye movements until there is complete immobility, accompanied by eyelid droop. It is also associated with accumulation of pigmented material on the membrane lining the eyes. Additional symptoms may include:

• Mild skeletal muscle weakness
• Heart block (a cardiac conduction defect)
• Short stature
• Hearing loss
• An inability to coordinate voluntary movements (ataxia)
• Impaired cognitive function
• Diabetes

Seizures are infrequent. Several endocrine disorders can be associated with KSS.

Treatment of KSS is symptomatic and supportive and involves multiple specialties depending on the organs involved. The most essential is a regular and long-term follow-up with cardiologists. Conduction problems of heart impulse like heart block may be treated with a pacemaker. Other consultations may include audiology, ophthalmology, endocrinology, neurology, and neuropsychiatry. Hearing aids may be required. There is typically no treatment for limitation in eye movement. Endocrine problems may be treated with drugs.

KSS is a slowly progressive disorder. The prognosis varies depending on the severity and the number of organs involved. Early diagnosis and periodic electrocardiograms (ECG) are important because heart block can cause death in 20 percent of individuals. Early pacemaker implantation can be of great benefit and offer a longer life expectancy in many individuals.