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Kearns-Sayre Syndrome
Kearns-Sayre Syndrome is a complex neuromuscular disorder, characterised and clinically diagnosed by the triad; appearing before age 20, progressive external ophthalmoplegia and pigmentary retinopathy.
Progressive external ophthalmoplegia (PEO) is characterised by weakened eye muscles and drooped eyelids (ptosis), while pigmentary retinopathy arises due to the degeneration and death of the photoreceptor cells in the retina to cause a speckled “salt-and-pepper” appearance1,2. This results in poor night-vision and progressive vision loss.
What causes Kearns-Sayre Syndrome?
Kearns-Sayre Syndrome belongs to a group of rare disorders known as mitochondrial encephalomyopathies, where the mitochondria, the component of the cell responsible for providing energy contains a mutation in its DNA. This means that there is insufficient energy available to the brain and muscles, and causes other symptoms to develop, for example poor cognitive function and kidney problems. Kearns-sayre syndrome is most commonly caused by a deletion mutation in the mitochondria DNA, where some important DNA and genetic information is missing.
Kearns-Sayre Syndrome develops most frequently after conception, when the male sperm and female egg cells fuse, due to a somatic mutation. Changes to the DNA and genetic material occurs in our body cells but not in the sperm and egg sex cells. Therefore, people who have Kearns-Sayre Syndrome caused in this way will not pass it to their children.
However, on rare occasions, Kearns-Sayre Syndrome can be inherited in a mitochondrial pattern of inheritance. Only female egg cells contribute mitochondrial DNA, while the male sperm cells do not. Therefore, the condition may present itself in every generation in a family but affected males will not pass it to their children. Read more about the different patterns of inheritance in our Genetics and Inheritance section.
Electrocardiograms and retinal imaging, such as fluorescein angiography are common diagnostic measures to detect Kearns-Sayre Syndrome, which screen for heart block and retinal pigment mottling respectively. The presence of the triad of symptoms is a key indication of Kearns-Sayre Syndrome.
What treatments are available?
Currently, treatments for Kearns-Sayre Syndrome are symptomatic, meaning they don’t target the underlying cause and the type of therapy depends on the symptoms and organs affected. A pacemaker is common among people with the condition who have heart block due to interferences with the nerve impulses. Regular consultations with your cardiologist (heart doctor) and ophthalmologist (eye doctor) are strongly recommended. Invasive surgical procedures can treat ptosis with an eye sling, although changes to the facial muscles can make it less effective.
References
1. National Institute of Health. Available at https://ghr.nlm.nih.gov/condition/kearns-sayre-syndrome. Accessed April 2020.
2. National Institute of Health. Available at https://rarediseases.info.nih.gov/diseases/6817/kearns-sayre-syndrome. Accessed April 2020.