Diabetes has a major negative impact on the clinical outcome of patients with CF. Although to a lesser extent, this has also been demonstrated in patients who show prediabetic alterations and who are at a high risk of developing diabetes. Identification of prediabetic CF patients may provide for improving or delaying clinical impairment (15). According to ISPAD guidelines (7), there are no consistent recommendations to determine whether insulin treatment should also be used for all INDET and IGT patients, as well as in the previous ISPAD 2014 guidelines (25). Through its promoting action on protein synthesis, Insulin, is known to improve nutritional and metabolic outcomes, and consequently lung function, even in patients with mild glycemic impairment. The IGT status indicates an insulin deficiency which leads to protein catabolism with a consequent negative impact on respiratory function by reducing diaphragm and intercostal muscle mass and strength. Early treatment with insulin could prevent this excessive catabolism (26). Although there was no clear indication to start insulin therapy in S., who resulted IGT at the OGTT carried out in 2016, we decided to treat him with insulin, considering the severity of his underlying condition. Before starting insulin therapy S. had frequent pulmonary flare-ups which required numerous hospitalizations for intravenous antibiotic therapy and had difficulty in gaining and maintaining weight. After the initiation of insulin therapy we reported an important reduction of pulmonary exacerbations, probably explained by positive effect of glargine on anabolic metabolism and respiratory muscles strength. This positive trend was also confirmed after the starting of modulator therapy (Lumacaftor/ Ivacaftor). Regarding pulmonary function, S. showed an encouraging increasing of FEV1 only in the first year of insulin therapy, then an unrelenting deterioration appeared due to the natural history of CF lung damage, despite the Lumacaftor/Ivacaftor therapy. Respect to the nutritional status a noticeable impairment in BMI z score occurred when overt diabetes appeared. The latter was probably secondary to the poor adherence to therapy, the loss of the father, and the physical inactivity due to the COVID-19 lockdown. This confirms that the IGT status represents a developmental risk factor in pediatric patients with CF. Furthermore, in this case it is conceivable that insulin glargine therapy has contributed preserving him from further clinical worsening, as we had observed in the previous years of COVID-19 pandemic.
According to the latest ISPAD guidelines, insulin therapy is the standard medical treatment in case of CFRD while it could be considered a choice in the case of prediabetic patients with CF showing significant comorbidities such as difficulty in maintaining weight, poor linear growth, frequent pulmonary exacerbations or worsening of lung function. However it is still debated whether to initiate insulin in patients with CF and prediabetes. Few studies on the use of insulin in prediabetic patients have been performed, demonstrating both therapeutic efficacy of insulin treatment (15; 27, 28) and not (9). However, the latter is a study including both adult and pediatric subjects. Our clinical case underlines the potential role of insulin in the early stages of glucose derangements, even before the diagnosis of CFRD, in a young patient with compromised clinical conditions. The diagnosis of CFRD was made 4 years after the initiation of insulin therapy when the worsening of glycemic control appeared. This was probably due to the association of several factors: poor therapeutic compliance, pulmonary exacerbation, excessive consumption of high-calorie foods and physical inactivity (due to the COVID-19 pandemic lockdown). It is reasonable to speculate that the early initiation of insulin therapy allowed to delay the onset of CFRD and to have a more indolent clinical course of the disease. However no sufficient evidence is available to demonstrate our hypothesis. Regarding treatment strategies in patients with CF and prediabetes, further investigations with observational trials are needed to confirm the usefulness of early insulin therapy in the prediabetes stage. Actually, two large studies are in progress to answer this question: “Cystic Fibrosis - Insulin Deficiency, Early Action” (ClinicalTrials.gov Identifier: NCT01100892) and “The Impact of Insulin Therapy on Protein Turnover in Pre-Diabetic Cystic Fibrosis Patients” (ClinicalTrials.gov Identifier: NCT02496780). The results of these studies will clarify if treatment of prediabetes in patients with CF is effective to delay the clinical decay of the underlying disease.
During the quarantine, diseases other than COVID-19 remained in the background and patients delayed their regular follow-up visits or did not worry about their symptoms aggravating the onset of many diseases as diabetic ketoacidosis. Blood glucose should be carefully monitored in diabetic patients with COVID19 infection as an increased risk of ketoacidosis has been reported in these patients (29). Even among patients hospitalized for COVID-19 and without a history of diabetes, an increased mortality rate and prolonged hospitalization were reported in those whose blood glucose levels had increased during the hospitalization period. These data suggest that keeping blood glucose within normal limits can reduce complications and mortality (30). In pediatric patients, comorbidities such as diabetes, chronic lung disease, tumors, immunodeficiencies, chronic renal failure, and neurological disorders may increase the morbidity-mortality risk related to COVID-19. These patients not only risk a more severe course of COVID19 infection, but also mismanagement of the underlying disease (31). To reduce this risk, specific follow-up paths should be ensured for these patients even during times of the pandemic. It is essential to avoid the interruption of care for chronic patients even by using alternative pathways such as telemedicine when regular follow-up cannot be guaranteed.