Pediatric Case Series of Cystic Fibrosis and Type 1 Diabetes Autoimmunity

Background: Diabetes is the most common comorbidity in individuals with cystic fibrosis (CF) Autoimmunity was reported to be no greater in CF related diabetes (CFRD) than in the general population and routine screening for type 1 diabetes (T1D) antibodies is not recommended. We report 3 patients with CF, diabetes and T1D autoimmunity.

Clinical cases: Patient 1 and 2 are Caucasian siblings with CF, genotype ∆F5homozygous and pancreatic insufficiency. Patient 1 is a male who presented at age 16 with polyuria, polydipsia and weight loss. Fasting glucose was 350 mg/dL. C peptide was 1.1 ng/ml and Hba1c was >14%. T1D antibodies showed (Anti GAD 147, negative Islet cell antigen antibody 512 (IA2), ZNT8 and insulin antibodies). Current insulin requirement at age 22 is 0.8 units/kg/day with Hba1C ranging from 6.7-12.0%. Patient 2 is a female diagnosed with CFRD at age 9 with an oral glucose tolerance test. Fasting glucose was 92 mg/dL and 2-hour glucose 209 mg/dL. C peptide 7.1 ng/ml. Hba1c 6.7%. T1D antibodies were negative at presentation. At age 14, because of increase in insulin requirement, T1D antibodies were retested and positive (Anti GAD 31, IA2 52, znt8 0.955). Her current insulin dose at age16 is 0.7units/kg/day with Hba1c ranging 6.7-12.7%. Patient 3 is a prepubertal biracial (African American, Caucasian) female with CF, genotype 1 copy of ∆F5and 1 copy of ∆I507, pancreatic insufficiency and Hashimoto’s hypothyroidism. She presented at age 9 with polyuria, polydipsia and weight loss. She was in DKA with glucose 686 mg/dL, bicarbonate 5 mEq/L, BOHB 5.4 mmol/L, C-Peptide 0.1 ng/ml, HbA1C >14%. T1D antibodies were positive (Anti GAD 192, IA2 183, ZnT8 0.177, Insulin 0.017). Current insulin dose at age 11 is 0.55 unit/kg/day with Hba1c ranging 7.7-10.2%.

Conclusion: T1D needs to be considered in a CF patient with hyperglycemia when patient is prepubertal, symptomatic, in DKA, or requiring high insulin doses. Correct diagnosis allows for proper treatment and help prevent short and long-term diabetes complications.