ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2019) 66 P34 | DOI: 10.1530/endoabs.66.P34

When one diagnosis just isn't enough - diabetes as a first presentation of cystic fibrosis

Meera Mallya1, Gunjan Jain1 & Peter Winocour2

1East and North Hertfordshire NHS Trust, Stevenage, UK; 2East and North Herts Institute of Diabetes and Endocrinology (ENHIDE), Welwyn Garden City, UK

Diabetes is a common presentation in children and young people. We describe a case of undiagnosed cystic fibrosis (CF), where diabetes was the presenting diagnosis. A 14 year old girl presented with a 2-month history of weight loss, abdominal pain, polyuria and polydipsia. Blood glucose was 31.4 mmol/l with ketones of 0.8 mmol/l, and a diagnosis of T1DM was made. Initial bloods showed HbA1c 150 mmol/mol, normal thyroid function, negative TTG, and negative TPO, GAD and IA2 antibodies. Her HbA1c remained well controlled for the next few years on MDI’s, at 42–51 mmol/mol. Recent urine C-peptide was 3.15 nmol/l, indicating preserved pancreatic beta-cell function 4 years after diagnosis of diabetes. At 16 years she noted that large meals caused diarrhoea and she had a persistent cough. At 17 years she presented with haemoptysis, and reported 6 months of productive cough, requiring recurrent antibiotics, with a 4-month history of weight loss. Chest X-ray suggested bronchiectatic changes and a high-resolution CT confirmed widespread cylindrical and cystic bronchiectasis. She was negative for HIV and TB, with a negative vasculitis screen and normal alpha-1-antitrypsin levels. Her lung function tests were normal, with good exercise tolerance. A genetic screen showed homozygous ▵ F508del, confirming the diagnosis of CF. Newborn screening for CF was fully introduced across the UK in 2007 and has helped in the early identification of children with CF. Most late onset (after 16 years) diagnoses of CF occur in people with compound heterozygote mutations, the majority presenting with respiratory complications. To our knowledge there are three case reports of children with diabetes as the presenting feature of CF. We describe an unusual case of an adolescent with homozygous ▵ F508del who presented initially with diabetes, before the respiratory manifestations of CF became apparent. In retrospect, respiratory and gastrointestinal symptoms were present previously. The lack of clear autoimmune features of T1DM should have raised the possibility of an alternative form of diabetes. It is therefore important to consider the possible diagnosis of CF in adolescents with diabetes who have associated respiratory or gastrointestinal symptoms, and who may have missed newborn screening, particularly with negative pancreatic beta-cell antibodies and high urine C-peptide.

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