Sir.—In their report in the June 1977 issue of the Journal of a patient with Kearns-Sayre syndrome, Seigel et al1 mention diabetes mellitus as a previously undescribed accompaniment of this condition.
We have seen three typical cases of Kearns-Sayre syndrome with progressive external ophthalmoplegia, retinal pigmentary degeneration, cardiac conduction defects, small stature, elevated CSF protein, and "ragged-red" fibers in a muscle biopsy specimen. In addition, two of these patients had ataxia, neurosensory hearing loss, and hypogonadism. In a girl, now 17 years old, diabetes mellitus was diagnosed at the age of 13 years. She was treated with diet and insulin. Fasting blood glucose values were also repeatedly elevated (135 to 150 mg/100 ml) in our second case, a young woman aged 21 years.
We are aware of six patients2-7 with Kearns-Sayre syndrome and chemical diabetes mellitus (elevated fasting blood glucose or abnormal glucose tolerance test). In addition