Characterization of a mitochondrial DNA deletion in patients with mitochondrial myopathy.

Kearns-Sayre syndrome (KSS) is the most commonly diagnosed mitochondrial myopathy and it produces severe neuromuscular symptoms. The most frequent cause is a mitochondrial DNA (mtDNA) deletion (common deletion) that removes a 4,977-bp segment of DNA that includes several genes encoding respiratory chain subunits. In this disorder, the population of deleted mtDNA molecules coexists with a population of normal, wild-type, full-length mtDNAs. We have performed a morphological study and a 3-primer polymerase chain reaction (PCR) on paraffin-embedded muscle tissues from two Korean KSS patients. Our results show that these patients have the essential clinical manifestations of KSS, as well as morphological evidence of mitochondrial myopathy. PCR analysis revealed the existence of two co-amplified fragments, the wild-type fragment having 152 bp and the deleted fragment having the 123 bp characteristic of common deletion. This study may provide valuable information for the molecular diagnosis of KSS in Koreans.