"One of my patients has CPEO, onset before 20 yrs of age (since childhood), pigment mottling retinopathy but no cardiac conduction defect. Please let me know: a) incidence of heart block in CPEO cases and in Kearns-Sayre syndrome (KSS) ; b) whether there is any chronological order of appearance of symptoms/signs in KSS (especially the triad). For my case, can conduction defect occur at any time and pose future problem?"

About 25% of patients get heart block, and other rhythm defects also occur. Heart block can occur at any time and there is not a specific order of appearance. - Burton J. Kushner, M.D.