Objective : Patients diagnosed with diabetes in their 2nd decade of life are often labelled as having Type 1 Diabetes Mellitus (T1DM). When insulin requirements become highly variable, additional testing becomes pertinent to re-evaluate the clinical picture. Cystic-fibrosis related diabetes (CFRD) can present similarly to T1DM. Patients with atypical cystic fibrosis without pulmonary manifestations can remain undiagnosed for years.
Methods : n/a
We present a 23-year-old female, diagnosed with T1DM at 16 years. The diagnosis was questioned when she had recurrent DKAs and hypoglycemic episodes with A1c of >14%, despite medication compliance and requiring insulin doses up to 2 units/kg/day (weight 30 kg, BMI < 19 kg/m2). Her failure to thrive and chronic diarrhea prompted additional evaluation. She had elevated liver enzymes and low C-peptide. Workup was negative for autoimmune T1DM, thyroid disease, adrenal insufficiency, celiac disease, autoimmune hepatitis, primary biliary cirrhosis, Wilson’s disease, HIV and immune deficiency. Abdominal US showed fatty liver disease. CT abdomen pelvis was negative for intraabdominal pathology. EGD and colonoscopy were unremarkable. She had increased fecal elastase indicating moderate pancreatic insufficiency. Initial sweat chloride test was positive at 90 mEq Cl/L while the second was equivocal at 41 mEq Cl/L. CFTR gene panel of 165 variants was negative.
She is on a fat-rich diet and supplementation with fat-soluble vitamins and pancreatic enzyme replacement. She gained 5kg in 2 months. Concurrently, her glycemic control improved without new incidences of DKA or hypoglycemia.
She has never had a hospital admission for respiratory infections. Chest imaging have shown no lung abnormalities. Pulmonary function testing is pending.
Cystic fibrosis (CF) typically presents with pulmonary manifestations in the early course, with CFRD occurring as a late complication. Atypical CF can present as dysfunction in one organ system, affecting gastrointestinal, endocrine or genitourinary systems. Atypical CF has been diagnosed in individuals as old as 70 years. Diagnosis requires symptomatic presentation and additional testing for sweat chloride, nasal potential difference and genetic analysis. Up to 15% of patients have rare or unidentified CFTR gene mutations. Management can prove challenging given pronounced stress hyperglycemia with high insulin requirements in acute exacerbations, which can cause hypoglycemia during the post-resolution phase. Recognizing atypical CF can prompt effective treatment in improving patient outcomes.
Endocrinology fellow with interest in oncologic endocrinology and lipidology