Long name: Kearns-Sayre Syndrome

KSS is a slowly progressive multi-system mitochondrial disease that often begins with drooping of the eyelids (ptosis). Other eye muscles eventually become involved, resulting in paralysis of eye movement. Degeneration of the retina usually causes difficulty seeing in dimly lit environments.

KSS is characterized by three main features:

Typical onset before age 20 although may occur in infancy or adulthood

Paralysis of specific eye muscles (called chronic progressive external ophthalmoplegia – CPEO)
Degeneration of the retina causing abnormal accumulation of pigmented (colored) material (pigmentary retinopathy)

In addition, one or more of the following conditions is present:

  • Block of electrical signals in the heart (cardiac conduction defects)
  • Elevated cerebrospinal fluid protein
  • Incoordination of movements (ataxia)


As with all mitochondrial diseases, there is no cure for KSS. Treatments are based on the types of symptoms and organs involved, and may include: Coenzyme Q10, insulin for diabetes, cardiac drugs, and a cardiac pacemaker which may be life-saving. Surgical intervention for drooping eyelids may be considered but should be undertaken by specialists in ophthalmic surgical centers.

KSS is slowly progressive and the prognosis varies depending on severity. Death is common in the third or fourth decade and may be due to organ system failures.

Cause: Most cases are due to large mitochondria DNA deletions

Links: https://rarediseases.info.nih.gov/diseases/6817/kearns-sayre-syndrome

Patients with KSS may also have such problems as deafness, dementia, kidney dysfunction, and muscle weakness. Endocrine abnormalities including growth retardation, short stature, or diabetes may also be evident. 

KSS is a rare disorder. It is usually caused by a single large deletion (loss) of genetic material within the DNA of the mitochondria (mtDNA), rather than in the DNA of the cell nucleus. These deletions, of which there are over 150 species, typically arise spontaneously. Less frequently, the mutation is transmitted by the mother.