A 15 year old boy with cystic fibrosis presents with a 3-6kg weight loss over the past month unaccompanied by changes in his pulmonary and gastrointestinal symptoms. You suspect that he has developed which of the following?

Diabetes mellitus is a common development in the adolescent and older patient with cystic fibrosis. It results from pancreatic fibrosis and beta-cell destruction. It behaves like maturity onset diabetes, with little tendency to ketoacidosis. Diabetes should always be considered when an older child with cystic fibrosis loses weight.