Clinical characteristics and disease severity of adults with cystic fibrosis with at least one residual function mutation

Abstract Rationale: Cystic fibrosis (CF) is a heterogeneous disease with most mutations resulting in defective or missing protein. However, some mutations permit a residual function. The present study aimed to assess disease severity and clinical features of CF adults with residual function mutation (RFM). Methods: A secondary analysis of the Milan Adult CF Database enrolling CF adults according to 2017 CF Foundation guidelines and followed up from 2006 to 2016 was conducted. Patients with ≥1 RFM (Group 1) and those with either F508del homozygosis or ≥1 class I mutation (Group 2) were selected. Results: Out of 325 patients, 69 (21%) and 90 (28%) were included in Group 1 and 2, respectively. Group 1 patients were older at CF diagnosis (29 VS. 2 years, P<0.0001), female (52% VS. 36%, P= 0.036), and more frequently referred from pulmonary clinics (47% VS. 11%, P<0.0001). Positive sweat test rate of both groups was similar (83% VS. 91%), whereas a borderline result was more frequent in Group 1 (14% VS. 3%, P= 0.017). Group 1 patients had higher median FEV1 (80% VS. 67%, P= 0.001) and lower prevalence of pancreatic insufficiency (10% VS. 82%, P<0.0001) and diabetes (6% VS. 34%, P<0.0001). Rates of any and P. aeruginosa chronic infection were comparable. 23% of patients in Group 1 had ≥3 exacerbations/year and 26% had ≥1 hospitalization/year. Macrolides (10% VS. 40%, P<0.0001) and inhaled antibiotics (29% VS. 62%, P<0.0001) were less frequently prescribed in Group 1. Conclusion: Although less severe than “typical” CF, adults with RFM should commence individualized care and follow-up. Footnotes Cite this article as: European Respiratory Journal 2018 52: Suppl. 62, PA1325.