Diabetes in pediatric patients with Kearns-Sayre syndrome: clinical presentation of 2 cases and a review of pathophysiology.

Kearns-Sayre syndrome (KSS), resulting from a mitochondrial DNA deletion, is a rare cause of diabetes in children. We report 2 pediatric cases of KSS associated with diabetes that presented with hyperosmolar hyperglycemia with minimal ketosis. Both patients were treated initially with isotonic fluid resuscitation followed by intravenous insulin infusion. The first case was a boy of Blackfoot Aboriginal ancestry who presented with failure to thrive, developmental delay and Fanconi syndrome and was diagnosed with KSS at 3 years of age. At 4 years he presented with a cough and left upper lobe lung infiltrate as well as a hyperosmolar hyperglycemic episode. He subsequently required multiple daily insulin injections. This patient developed cardiomyopathy and died at the age of 10 years. The second case was a 6-year-old boy of Asian ancestry who presented with ataxia exacerbated by intercurrent illnesses, decreased exercise tolerance, gross motor and fine motor delays, anorexia and recurrent episodes of vomiting associated with dehydration, and he was subsequently diagnosed with KSS. At 11 years of age, the patient developed hyperosmolar hyperglycemia, and after treatment for it, he required multiple daily insulin injections. He died of end stage congestive heart failure secondary to cardiomyopathy at 13 years of age. These 2 cases are presented to describe the possible pathophysiology of mitochondrial diabetes and to emphasize the need to monitor for the development of diabetes in patients with known mitochondrial disease and also to be aware of possible mitochondrial disease in pediatric patients who present with hyperglycemia in the context of multisystem involvement.