Kayrnes- Sayre Syndrome, glucagon production in pancreas

A photomicrograph of a section through the pancreas of a patient suffering from Kayrnes-Sayre Syndrome. The brown cells are secreting glucagon. The disease is due to a mutation in mitochondrial DNA, and leads to muscle weaknesses, retarded growth and diabetes. There is reduction of islet mass and size and very few beta-cells, probably due to abnormal islet development.