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Pediatric geneticist, pediatrician

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Kearns-Sayre syndrome

Alexey Kryvenko, medical expert
Last reviewed: 05.07.2025

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Kearns-Sayre syndrome - this disease was first described in 1958. Most cases are caused by large mtDNA deletions of 2-10 thousand bp. The most common deletion is 4977 bp. Duplications or point mutations are extremely rare.

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Causes of Kearns-Sayre Syndrome

Most cases of Kearns-Sayre syndrome are sporadic, which can be explained by the high rate of mutation of the mitochondrial genome. It is assumed that deletions most often occur in the mitochondria of somatic cells during early embryonic development. In almost 50% of cases, patients have, along with this mutation, a duplication of the D-loop inherited from the mother. The genes abnormally fused as a result of the deletion can be transcribed, but are not capable of translation, and, consequently, a deficiency of the encoded proteins develops.

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Symptoms of Kearns-Sayre Syndrome

The disease manifests itself at the age of 4-20 years and includes a triad of symptoms:

ophthalmoplegia with ptosis of the upper eyelid and limited movement of the eyeballs;
progressive weakness of the muscles of the proximal extremities;
pigmentary degeneration of the retina.

As Kearns-Sayre syndrome progresses, other symptoms join in: damage to the heart (rhythm disturbance, atrioventricular block, ventricular dilation), hearing organ (sensorineural deafness), visual organ (optic nerve atrophy), and decreased intelligence. Patients die from cardiovascular failure 10-20 years after the onset of the disease. Laboratory tests reveal lactic acidosis and increased 3-hydroxybutyrate in the blood; morphological examination of muscle tissue biopsies reveals the RRF phenomenon (ragged muscle fibers).

Diagnosis of Kearns-Sayre syndrome

The diagnosis is clarified by molecular genetic testing and detection of a large deletion in mtDNA. However, when analyzing the data obtained, it is necessary to take into account the existence of heteroplasmy; peripheral blood cells contain only about 5% mutant DNA. More information can be obtained from molecular genetic analysis of muscle biopsies, which contain up to 70% mutant mitochondrial DNA.

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