The clinical diagnosis and molecular genetics of kearns-sayre syndrome: a complex mitochondrial encephalomyopathy.

From the first description by Kearns and Sayre in 1958, this syndrome has been diagnosed in several hundred patients. However, the labile character of its clinical manifestations makes diagnosis difficult and delayed. Only recently, some thirty years from the first diagnosis, have we recognized mitochondrial DNA rearrangements as the molecular basis of the disease. This has lead to increasing interest in the contribution which mtDNA deletions make to Kearns-Sayre Syndrome (KSS) and other disorders. Although the true prevalence of this syndrome in the general population is unknown, a basic awareness of the KSS phenotype, as well as of the essential elements of patient evaluation is important for appropriate patient management. Although methods of assessing patients for mtDNA rearrangements are well developed, ambiguity in patient diagnosis often remains even after detailed, multisystem testing. Advances in our understanding of the genetic background and the tissue specific effects of mtDNA deletions, in addition to resolving the inheritance pattern, will also increase our ability to diagnose, manage and counsel patients with this disorder.