Rationale: Early onset and progression of lung disease in children with cystic fibrosis (CF) indicates that sensitive noninvasive outcome measures are needed for diagnostic monitoring and early intervention clinical trials. The lung clearance index (LCI) and chest magnetic resonance imaging (MRI) were shown to detect early lung disease in CF; however, the relationship between the two measures remains unknown. Objectives: To correlate the LCI with abnormalities detected by MRI and compare the sensitivity of the two techniques to detect responses to therapy for pulmonary exacerbations in children with CF. Methods: LCI determined by age-adapted multiple breath washout techniques and MRI studies were performed in 97 clinically stable children with CF across the pediatric age range (0.2–21.1 yr). Furthermore, LCI (n = 26) or MRI (n = 10) were performed at the time of pulmonary exacerbation and after antibiotic therapy. MRI was evaluated using a dedicated morphofunctional score. Measurements and Main Results: The LCI correlated with the global MRI score as well as MRI-defined airway wall abnormalities, mucus plugging, and abnormal lung perfusion in infants and toddlers (P < 0.05 to P < 0.001) and in older children (P < 0.001) with CF. LCI and MRI were sensitive to detect response to antibiotic therapy for pulmonary exacerbations. Conclusions: Our results indicate that LCI and MRI may be useful complementary tools for noninvasive monitoring and as quantitative endpoints in early intervention trials in children with CF. In this context, MRI enables detection of disease heterogeneity, including regional mucus plugging associated with abnormal lung perfusion in early CF lung disease. Clinical trial registered with www.clinicaltrials.gov (NCT 02270476).

Background: Pulmonary alveolar proteinosis (PAP) is a heterogeneous condition with more than 100 different underlying disorders that need to be differentiated to target therapeutic options, which are generally limited.Methods: The clinical course of two brothers with pathogenic variants in the methionyl‐tRNA synthetase (MARS)1 gene was compared to previously published patients. Functional studies in patient‐derived fibroblasts were performed and therapeutic options evaluated.Results: The younger brother was diagnosed with PAP at the age of 1 year. Exome sequencing revealed the homozygous MARS1 variant p.(Arg598Cys), leading to interstitial lung and liver disease (ILLD). At 2 years of age, following surgery hypoglycemia was detected, the pulmonary condition deteriorated, and the patient developed multiorgan failure. Six therapeutic whole lung lavages (WLL) were necessary to improve respiratory insufficiency. Methionine supplementation was started and a high protein diet ensured, leading to complete respiratory recovery. The older brother, homozygous for the same MARS1 variant, had a long‐known distinct eating preference of methionine‐rich food and showed a less severe clinical phenotype. Decreased aminoacylation activity confirmed the pathogenicity of p.(Arg598Cys) in vitro. In agreement with our review of currently published ILLD patients, the presence of hepatopathy, developmental delay, muscular hypotonia, and anemia support the multisystemic character of the disease.Conclusions: Catabolic events can provoke a severe deterioration of the pulmonary situation in ILLD with a need for repetitive WLL. Although the precise role of oral methionine supplementation and high protein intake are unknown, we observed an apparent treatment benefit, which needs to be evaluated systematically in controlled trials.

Background: We recently demonstrated that elexacaftor/tezacaftor/ivacaftor (ETI) improves the lung clearance index (LCI) and abnormalities in lung morphology detected by magnetic resonance imaging (MRI) in adolescent and adult patients with cystic fibrosis (CF). However, real-world data on the effect of ETI on these sensitive outcomes of lung structure and function in school-age children with CF have not been reported. The aim of this study was therefore to examine the effect of ETI on the LCI and the lung MRI score in children aged 6–11 years with CF and one or twoF508delalleles.Methods: This prospective, observational, multicentre, post-approval study assessed the longitudinal LCI up to 12 months and the lung MRI score before and 3 months after initiation of ETI.Results: A total of 107 children with CF including 40 heterozygous forF508deland a minimal function mutation (F/MF) and 67 homozygous forF508del(F/F) were enrolled in this study. Treatment with ETI improved the median (interquartile range (IQR)) LCI in F/MF (−1.0 (−2.0– −0.1); p<0.01) and F/F children (−0.8 (−1.9– −0.2); p<0.001) from 3 months onwards. Further, ETI improved the median (IQR) MRI global score in F/MF (−4.0 (−9.0–0.0); p<0.01) and F/F children (−3.5 (−7.3– −0.8); p<0.001).Conclusions: ETI improves early abnormalities in lung ventilation and morphology in school-age children with CF and at least oneF508delallele in a real-world setting. Our results support early initiation of ETI to reduce or even prevent lung disease progression in school-age children with CF.