Cystic fibrosis diagnosed in a black adolescent with long-standing, unstable diabetes mellitus.

A case is reported of a black youth whose marked diabetic lability was stabilized subsequent to establishing the diagnosis of cystic fibrosis and treatment of the pancreatic exocrine deficiency. The patient had no evidence of pulmonary involvement secondary to cystic fibrosis, but had a partial immunoglobulin A deficiency. A possible common etiology for diabetes mellitus and cystic fibrosis is discussed.