Maturity-onset diabetes of the young: Different diabetes in an infant with cystic fibrosis

Clinical and genetic features of maturity-onset diabetes of the young in pediatric patients: a 12-year monocentric experience

BACKGROUND

A retrospective observational study was conducted to assess the prevalence of maturity onset diabetes of the young (MODY) in a large paediatric population of Southern Italy newly diagnosed with diabetes. Clinical and genetic features of the identified MODY patients were also described.

METHODS

Genetic testing was performed in children and adolescents newly diagnosed with diabetes who presented autoantibody negativity and fasting C-peptide levels ≥ 0.8 ng/mL. Patients with a low insulin daily dose and optimal glycaemic control after two years from diabetes onset were also investigated for monogenic diabetes, regardless of their autoimmunity status and/or C-peptide levels.

RESULTS

A prevalence of 6.5% of MODY was found. In particular, glucokinase-MODY was the most common type of MODY. The mean age at diagnosis was 9.1 years. Clinical presentation and biochemical data were heterogeneous also among patients belonging to the same MODY group.

CONCLUSIONS

We found a relatively high prevalence of MODY among paediatric patients with a new diagnosis of diabetes in comparison to literature data. Our findings highlight that a more detailed clinical evaluation along with easier and less expensive approachability to genetic testing may allow diagnosing an increasing number of MODY cases. A correct, prompt diagnosis is crucial to choose the most appropriate treatment and offer adequate genetic counselling.

Cystic Fibrosis-Related Diabetes (CFRD): Overview of Associated Genetic Factors

Cystic fibrosis (CF) is the most common autosomal recessive disease in the Caucasian population and is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene that encodes for a chloride/bicarbonate channel expressed on the membrane of epithelial cells of the airways and of the intestine, as well as in cells with exocrine and endocrine functions. A common nonpulmonary complication of CF is cystic fibrosis-related diabetes (CFRD), a distinct form of diabetes due to insulin insufficiency or malfunction secondary to destruction/derangement of pancreatic betacells, as well as to other factors that affect their function. The prevalence of CFRD increases with age, and 40–50% of CF adults develop the disease. Several proposed hypotheses on how CFRD develops have emerged, including exocrine-driven fibrosis and destruction of the entire pancreas, as well as contrasting theories on the direct or indirect impact of CFTR mutation on islet function. Among contributors to the development of CFRD, in addition to CFTR genotype, there are other genetic factors related and not related to type 2 diabetes. This review presents an overview of the current understanding on genetic factors associated with glucose metabolism abnormalities in CF.

Monogenic Diabetes in a Child with Cystic Fibrosis: A Case Report and Review of the Literature

Cystic fibrosis-related diabetes (CFRD) is associated with worsening pulmonary function, lower body mass index, increased infection frequency, and earlier mortality. While the incidence of CFRD is rising, its development in patients under the age of 10 years is uncommon. We present a 9-year-old girl with cystic fibrosis (CF) who presented with a 5-year history of nonprogressive hyperglycemia, demonstrated by abnormal oral glucose tolerance tests, glycated hemoglobin A1c (HbA1c) levels consistently >6.5%, and negative pancreatic autoantibodies. Subsequent genetic testing revealed a pathogenic heterozygous recessive mutation in the GCK gene at c.667G>A (p.Gly223Ser), consistent with a diagnosis of GCK-MODY. Significant dysglycemia in young children with CF should raise suspicion for alternative etiologies of diabetes and warrants further investigation. The clinical impact of underlying monogenic diabetes in patients with CF is unclear, and close follow-up is warranted. This case also offers unique insight on the impact of hyperglycemia in the absence of insulin deficiency on CF-specific outcomes.