Kearns-Sayre syndrome with sideroblastic anemia: molecular investigations.

The progressive syndrome of Kearns-Sayre has been studied at the clinical, biochemical and genetic levels in a patient. Clinical arguments suggest an evolution from Pearson's disease to Kearns-Sayre syndrome. The respiratory chain activities were low, and Southern blot analysis, together with gene sequencing, showed a heteroplasmic deletion of 7767 base pairs in a significant proportion of the mitochondrial DNA in different tissues. Protein synthesis studies on lymphoblasts did not reveal any translation of the new reading frame created by the deletion, although the corresponding deleted mitochondrial DNA sequence is transcribed.