OBJECTIVE:

To differentiate the insulin-dependent glucose intolerance associated with cystic fibrosis from type I diabetes mellitus in patients with cystic fibrosis.

DESIGN:

Patient report.

SETTING:

Tertiary care referral center.

PARTICIPANT:

An 11-year-old boy with cystic fibrosis who developed diabetic ketoacidosis. MEASUREMENT/MAIN RESULT: Biochemical, immunologic, and molecular techniques were used to support the sporadic association of type I diabetes mellitus in a patient with cystic fibrosis. Cystic fibrosis was confirmed by sweat test and further supported by the demonstration of a heterozygous deletion of the F508 locus. Evidence for the diagnosis of type I diabetes mellitus was developed from the clinical presentation of diabetic ketoacidosis with hyperglycemia, ketonemia, and ketonuria. Immunologic evidence included the demonstration of anti-insulin antibodies. The demonstration of homozygous absence of aspartic acid at position 57 of the HLA DQ-beta chain placed this child at high risk of type I diabetes mellitus.

CONCLUSION:

The clinical presentation and the presence of immunologic and genetic markers characteristic of type I diabetes mellitus supports the concordance of cystic fibrosis and type I diabetes mellitus in this patient.