Deletions of mitochondrial DNA in Kearns-Sayre syndrome (Reprinted from Neurology, vol 38, pg 1339-1346, 1988)

We have identified large-scale deletions in muscle mitochondrial DNA (mtDNA ) in seven of seven patients with Kearns-Sayre syndrome (KSS). We found no detectable deletions in the mtDNA of ten non-KSS patients with other mitoch ondrial myopathies or encephalomyopathies, or three normal controls. The de letions ranged in size from 2.0 to 7.0 kb, and did not localize to any sing le region of the mitochondrial genome. The proportion of mutated genomes in each KSS patient ranged from 45% to 75% of total mtDNA. There was no corre lation between the size or site of the deletion, biochemical abnormality of mitochondrial enzymes, or clinical severity. The data bolster arguments th at KSS is a unique disorder and genetic in origin.