Cairns-Seir Syndrome

Cairns-Seyr syndrome - this disease was first described in 1958. The majority of cases are caused by large deletions of mtDNA with a length of 2-10 thousand bp. The most widespread deletion is 4977 bp long. Extremely rare are duplications or point mutations.

[1], [2], [3], [4]

Causes of Cairns-Seir syndrome

The majority of cases of the Cairns-Seir syndrome are sporadic, which can be explained by the high rate of mutation of the mitochondrial genome. It is suggested that deletions most often occur in mitochondria of somatic cells in the period of early embryonic development. Almost 50% of patients have along with this mutation the duplication of the D-loop, inherited from the mother. Abnormally fused as a result of deletion, genes can be transcribed, but not translationally and, consequently, deficiency of encoded proteins develops.

[5], [6], [7], [8], [9], [10], [11]

Symptoms of Cairns-Seir syndrome

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

• ophthalmoplegia with ptosis of the upper eyelid and restriction of movements of the eyeballs;
• Progressive weakness of the muscles of the proximal parts of the limbs;
• pigmentary degeneration of the retina.

As the progression of the Kerns-Seir syndrome joins other symptoms: heart disease (rhythm disturbance, atrioventricular block, expansion of the ventricular cavity), hearing organ (neurosensory deafness), vision organ (optic nerve atrophy), intelligence decreases. Patients die from cardiovascular failure 10-20 years after the onset of the disease. At laboratory research reveal: lactate-acidosis and increase of 3-hydroxybutyrate in blood; the morphological study of muscle biopsy specimens reveals the phenomenon of RRF ("ripped" muscle fibers).

Diagnosis of Cairns-Seir syndrome

The diagnosis is clarified by molecular-genetic research 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, in peripheral blood cells only about 5% of the mutant DNA is contained. Much information can be obtained by molecular genetic analysis of muscle biopsies, which contain up to 70% of mitochondrial mutant DNA.

[12], [13], [14],