Heredity of mitochondrial ocular myopathy and Kearns Sayre syndrome

Abstract

Mitochondrial ocular myopathy (OM) has an infantile onset variant with widespread disease, known as Kearns Sayre syndrome (KSS). Evidence for transmission of the disease from one generation to the other has been denied, especially for KSS. There is however plenty evidence for this transmission from the literature, even for KSS. KSS patients have however a low fertility, so transmission of a KSS picture from parent to child has only scarcely been reported.

A mitochondrial inheritance has been claimed but proved to be very unlikely, because of absence of predominant maternal inheritance. Recently, deletions in mitochondrial DNA have been described exclusively in mitochondrial OM and especially KSS patients. In KSS the deletions were apparent in all affected tissues. There is up to now no conclusive evidence that the deletions are pathogenetically linked to OM and KSS, because of the absence of correlation between size and site of the deletions and the mitochondrial enzymatic deficiency or clinical severity. Moreover, not in all KSS patients and only in a minority of mitochondrial OM were the deletions found. The probability of an epiphenomenon remains but the finding of mtDNA deletions proves the nosological entity and specificity of mtOM and KSS.

Key Words:

• heredity
• mitochondria
• Kearns Sayre syndrome