Kearns-Sayre syndrome (KSS) is an extremely rare neuromuscular disorder that is the result of abnormalities in the DNA of mitochondria.

Mitochondria are small rod-like structures found in every cell of the body that produce the energy that drives cellular functions. The mitochondrial diseases correlate with specific DNA mutations that cause problems with many of the organs and tissues in the body.

Kearns–Sayre syndrome occurs spontaneously in the majority of cases. In some cases it has been shown to be inherited. There is no preference for race or sex, and there are no known risk factors. Onset of KSS happens usually before the age of 20.

KSS is characterized by progressive limitation of eye movements until there is complete immobility, accompanied by eyelid droop. It is also associated with abnormal 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 (infrequent)

Several endocrine disorders can be associated with KSS.

The prognosis for individuals with KSS varies depending on the severity of symptoms. KSS is a slowly progressive disorder.

Treatment for KSS is generally symptomatic and supportive. Because it is a rare condition, there are only case reports of treatments with very little data to support their effectiveness. Cardiac abnormalities may be treated with various cardiac drugs or a pacemaker.