Key inflammatory markers in bronchoalveolar lavage predict bronchiectasis progression in young children with CF.

INTRODUCTION: Inflammation appears early in cystic fibrosis (CF) pathogenesis, with specific elevated inflammatory markers in bronchoalveolar lavage fluid (BALF) correlating with structural lung disease. Our aim was to identify markers of airway inflammation able to predict bronchiectasis progression over two years with high sensitivity and specificity. METHODS: Children with CF with two chest computed tomography (CT) scans and bronchoscopies at a two-year interval were included (n= 10 at 1 and 3 years and n= 27 at 3 and 5 years). Chest CTs were scored for increase in bronchiectasis (Δ%Bx), using the PRAGMA-CF score. BALF collected with the first CT scan were analyzed for neutrophil% (n= 36), myeloperoxidase (MPO) (n= 25), neutrophil elastase (NE) (n= 26), and with a protein array for inflammatory and fibrotic markers (n= 26). RESULTS: MPO, neutrophil%, and inducible T-cell costimulator ligand (ICOSLG), but not clinical characteristics, correlated significantly with Δ%Bx. Evaluation of neutrophil%, NE, MPO, interleukin-8 (IL-8), ICOSLG, and hepatocyte growth factor (HGF), for predicting an increase of > 0.5% of Δ%Bx in two years, showed that IL-8 had the best sensitivity (82%) and specificity (73%). Neutrophil%, ICOSLG and HGF had sensitivities of 85, 82, and 82% and specificities of 59, 67 and 60%, respectively. The odds ratio for risk of >0.5% Δ%Bx was higher for IL-8 (12.4) than for neutrophil%, ICOSLG, and HGF (5.9, 5.3, and 6.7, respectively). Sensitivity and specificity were lower for NE and MPO). CONCLUSIONS: High levels of IL-8, neutrophil%, ICOSGL and HGF in BALF may be good predictors for progression of bronchiectasis in young children with CF.

Diagnostic challenges in CFTR-related metabolic syndrome: Where the guidelines fall short.

Newborn screening (NBS) for cystic fibrosis (CF) has enabled earlier diagnosis and has improved nutritional and growth-related outcomes in children with CF. For those with a positive NBS for CF that do not meet the diagnostic criteria for CF, the clinical entity called CFTR-Related Metabolic Syndrome (CRMS) or CF Screen- Positive, Inconclusive Diagnosis (CFSPID) is used. Although most children with CRMS remain relatively asymptomatic, studies have shown that between 11% and 48% of these patients may eventually progress to a diagnosis of CF over time. Although the CF Foundation guidelines for CRMS management and European CF Society guidelines for CFSPID have some similarities, there are also some differences. Here, we review challenging case scenarios that highlight remaining gaps in CRMS guidelines, thus supporting the need to update and unify existing guidelines.

Sweat induction using Pilocarpine microneedle patches for sweat testing in healthy adults.

BACKGROUND: The sweat test using pilocarpine iontophoresis remains the gold standard for diagnosing cystic fibrosis, but access and reliability are limited by specialized equipment and insufficient sweat volume collected from infants and young children. These shortcomings lead to delayed diagnosis, limited point-of-care applications, and inadequate monitoring capabilities. METHODS: We created a skin patch with dissolvable microneedles (MNs) containing pilocarpine that eliminates the equipment and complexity of iontophoresis. Upon pressing the patch to skin, the MNs dissolve in skin to release pilocarpine for sweat induction. We conducted a non-randomized pilot trial among healthy adults (clinicaltrials.gov, NCT04732195) with pilocarpine and placebo MN patches on one forearm and iontophoresis on the other forearm, followed by sweat collection using Macroduct collectors. Sweat output and sweat chloride concentration were measured. Subjects were monitored for discomfort and skin erythema. RESULTS: Fifty paired sweat tests were conducted in 16 male and 34 female healthy adults. MN patches delivered similar amounts of pilocarpine into skin (1.1 ± 0.4 mg) and induced equivalent sweat output (41.2 ± 25.0 mg) compared to iontophoresis (1.2 ± 0.7 mg and 43.8 ± 32.3 mg respectively). Subjects tolerated the procedure well, with little or no pain, and only mild transient erythema. Sweat chloride concentration measurements in sweat induced by MN patches (31.2 ± 13.4 mmol/L) were higher compared to iontophoresis (24.0 ± 13.2 mmol/L). Possible physiological, methodological, and artifactual causes of this difference are discussed. CONCLUSIONS: Pilocarpine MN patches present a promising alternative to iontophoresis to enable increased access to sweat testing for in-clinic and point-of-care applications.

Nasal airway inflammatory responses and pathogen detection in infants with cystic fibrosis.

BACKGROUND: Detecting airway inflammation non-invasively in infants with cystic fibrosis (CF) is difficult. We hypothesized that markers of inflammation in CF [IL-1ß, IL-6, IL-8, IL-10, IL-17A, neutrophil elastase (NE) and tumor necrosis factor (TNF-α)] could be measured in infants with CF from nasal fluid and would be elevated during viral infections or clinician-defined pulmonary exacerbations (PEx). METHODS: We collected nasal fluid, nasal swabs, and hair samples from 34 infants with CF during monthly clinic visits, sick visits, and hospitalizations. Nasal fluid was isolated and analyzed for cytokines. Respiratory viral detection on nasal swabs was performed using the Luminex NxTAG® Respiratory Pathogen Panel. Hair samples were analyzed for nicotine concentration by reverse-phase high-performance liquid chromatography. We compared nasal cytokine concentrations between the presence and absence of detected respiratory viruses, PEx, and smoke exposure. RESULTS: A total of 246 samples were analyzed. Compared to measurements in the absence of respiratory viruses, mean concentrations of IL-6, IL-8, TNF-α, and NE were significantly increased while IL-17A was significantly decreased in infants positive for respiratory viruses. IL-17A was significantly decreased and NE increased in those with a PEx. IL-8 and NE were significantly increased in infants with enteric pathogen positivity on airway cultures, but not P. aeruginosa or S. aureus. Compared to those with no smoke exposure, there were significantly higher levels of IL-6, IL-10, and NE in infants with detectable levels of nicotine. CONCLUSIONS: Noninvasive collection of nasal fluid may identify inflammation in infants with CF during changing clinical or environmental exposures.

Pulmonary exacerbations in early cystic fibrosis lung disease are marked by strong modulation of CD3 and PD-1 on luminal T cells.

Background: In chronic cystic fibrosis (CF) lung disease, neutrophilic inflammation and T-cell inhibition occur concomitantly, partly due to neutrophil-mediated release of the T-cell inhibitory enzyme Arg1. However, the onset of this tonic inhibition of T cells, and the impact of pulmonary exacerbations (PEs) on this process, remain unknown. Methods: Children with CF aged 0-5 years were enrolled in a longitudinal, single-center cohort study. Blood (n = 35) and bronchoalveolar lavage (BAL) fluid (n = 18) were collected at stable outpatient clinic visits or inpatient PE hospitalizations and analyzed by flow cytometry (for immune cell presence and phenotype) and 20-plex chemiluminescence assay (for immune mediators). Patients were categorized by PE history into (i) no prior PE, (ii) past history of PE prior to stable visit, or (iii) current PE. Results: PEs were associated with increased concentration of both pro- and anti-inflammatory mediators in BAL, and increased neutrophil frequency and G-CSF in circulation. PE BAL samples showed a trend toward an increased frequency of hyperexocytic "GRIM" neutrophils, which we previously identified in chronic CF. Interestingly, expression levels of the T-cell receptor associated molecule CD3 and of the inhibitory programmed death-1 (PD-1) receptor were respectively decreased and increased on T cells from BAL compared to blood in all patients. When categorized by PE status, CD3 and PD-1 expression on blood T cells did not differ among patients, while CD3 expression was decreased, and PD-1 expression was increased on BAL T cells from patients with current PE. Conclusions: Our findings suggest that airway T cells are engaged during early-life PEs, prior to the onset of chronic neutrophilic inflammation in CF. In addition, increased blood neutrophil frequency and a trend toward increased BAL frequency of hyperexocytic neutrophils suggest that childhood PEs may progressively shift the balance of CF airway immunity towards neutrophil dominance.

Cryoextraction via flexible bronchoscopy in children with tracheobronchial obstruction.

BACKGROUND: Cryoextraction via flexible bronchoscopy (FB) can be used to alleviate airway obstruction due to blood clots, casts, mucus, and foreign bodies. There is limited literature regarding the utility of cryoextraction to restore airway patency in critically ill children, especially on extracorporeal membrane oxygenation (ECMO). The aims of this study were to describe the clinical course and outcomes of children who underwent cryoextraction via FB. METHODS: A singlecenter retrospective review of children who underwent cryoextraction via FB between 2017 and 2021 was conducted. The analyzed data included diagnoses, indications for cryoextraction, respiratory support modalities, FB and chest imaging results, and outcomes. RESULTS: Eleven patients aged 3-17 years underwent a total of 33 cryoextraction sessions via FB. Patients required ECMO (n = 9) or conventional mechanical ventilation (CMV) for pneumonia, pulmonary hemorrhage, pulmonary embolism, asthma exacerbation, and cardiorespiratory failure following cardiac surgery. One patient underwent elective FB and cryoextraction for plastic bronchitis. Indications for cryoextraction included airway obstruction due to tracheobronchial thrombi (n = 8), mucus plugs (n = 1), or plastic bronchitis (n = 2). Cryoextraction via FB was performed on patients on ECMO (n = 9) and CMV (n = 2) with 6 patients requiring ≥3 cryoextraction sessions for airway obstruction. There were no complications related to cryoextraction. Patient outcomes included partial (n = 5) or complete (n = 6) restoration of airway patency with ECMO decannulation (n = 5) and death (n = 4) due to critical illness. CONCLUSIONS: Cryoextraction via FB is an effective intervention that can be utilized in critically ill children with refractory tracheobronchial obstruction to restore airway patency and to facilitate liberation from ECMO.

Impact of viral respiratory infections on pulmonary exacerbations in children with cystic fibrosis.

BACKGROUND: Viral respiratory infections trigger pulmonary exacerbations (PEs) in children with cystic fibrosis (CF), but their clinical impact is not well understood. METHODS: A retrospective review of pediatric patients with CF who underwent nasopharyngeal respiratory viral panel testing during hospitalization for a PE between 2011 and 2018 was conducted. Patients were dichotomized into viral-positive and viral-negative groups. The results of spirometry, respiratory cultures, duration of hospitalization, and risk for subsequent PEs were analyzed. RESULTS: Ninety-five patients had 210 hospitalizations for PE (viral-positive = 71/210, 34%) during the study period. Rhinovirus/enterovirus was the most common virus (52/71, 73%) identified. Viral-positive patients were younger (p < 0.001), had higher baseline forced expiratory volume in 1 s (FEV1) (p = 0.037), continued to maintain higher FEV1 at 3 and 6 months following PE (p = 0.003 and 0.002, respectively), and had a shorter duration of hospitalization (p = 0.006) compared to the viral-negative group. There was no difference between the two groups in the rate of recovery of FEV1 at 3 and 6 months following PE (p = 0.71 and 0.405, respectively), time to the next PE (hazard ratio = 1.34, p = 0.157), number of subsequent PEs in 6 months (p = 0.99), or Pseudomonas aeruginosa (PA) acquisition (p = 0.707). CONCLUSIONS: In this single pediatric CF center cohort, one-third of PEs requiring hospitalization were associated with a viral infection, with rhinovirus/enterovirus being the most common. Viral-positive PEs were not associated with a greater decline or delayed recovery of lung function, increased risk for PA acquisition, shortened duration to next PE, longer hospital stay, or an increase in the frequency of subsequent PEs in 6 months compared to viral-negative PEs.

Macrophage PD-1 associates with neutrophilia and reduced bacterial killing in early cystic fibrosis airway disease.

BACKGROUND: Macrophages are the major resident immune cells in human airways coordinating responses to infection and injury. In cystic fibrosis (CF), neutrophils are recruited to the airways shortly after birth, and actively exocytose damaging enzymes prior to chronic infection, suggesting a potential defect in macrophage immunomodulatory function. Signaling through the exhaustion marker programmed death protein 1 (PD-1) controls macrophage function in cancer, sepsis, and airway infection. Therefore, we sought to identify potential associations between macrophage PD-1 and markers of airway disease in children with CF. METHODS: Blood and bronchoalveolar lavage fluid (BALF) were collected from 45 children with CF aged 3 to 62 months and structural lung damage was quantified by computed tomography. The phenotype of airway leukocytes was assessed by flow cytometry, while the release of enzymes and immunomodulatory mediators by molecular assays. RESULTS: Airway macrophage PD-1 expression correlated positively with structural lung damage, neutrophilic inflammation, and infection. Interestingly, even in the absence of detectable infection, macrophage PD-1 expression was elevated and correlated with neutrophilic inflammation. In an in vitro model mimicking leukocyte recruitment into CF airways, soluble mediators derived from recruited neutrophils directly induced PD-1 expression on recruited monocytes/macrophages, suggesting a causal link between neutrophilic inflammation and macrophage PD-1 expression in CF. Finally, blockade of PD-1 in a short-term culture of CF BALF leukocytes resulted in improved pathogen clearance. CONCLUSION: Taken together, these findings suggest that in early CF lung disease, PD-1 upregulation associates with airway macrophage exhaustion, neutrophil takeover, infection, and structural damage.

Pilot study of inflammatory biomarkers in matched induced sputum and bronchoalveolar lavage of 2-year-olds with cystic fibrosis.

BACKGROUND: In this pilot study, we investigated whether induced sputum (IS) could serve as a viable alternative to bronchoalveolar lavage (BAL) and yield robust inflammatory biomarkers in toddlers with cystic fibrosis (CF) featuring minimal structural lung disease. METHODS: We collected IS, BAL (right middle lobe and lingula), and blood, and performed chest computed tomography (CT) scans from 2-year-olds with CF (N = 11), all within a single visit. Inflammatory biomarkers included 20 soluble immune mediators and neutrophil elastase (NE), as well as frequency and phenotype of T cells, monocytes/macrophages, and neutrophils. RESULTS: At the molecular level, nine mediators showed similar levels in IS and BAL (CXCL1, CXCL8, IL-1α, IL-1RA, IL-6, CCL2, CXCL10, M-CSF, VEGF-A), four were higher in IS than in BAL (CXCL5, IL-1ß, CXCL11, TNFSF10), and two were present in IS, but undetectable in BAL (IL-10, IFN-γ). Meanwhile, soluble NE had lower activity in IS than in BAL. At the cellular level, T-cell frequency was lower in IS than in BAL. Monocytes/macrophages were dominant in IS and BAL with similar frequencies, but differing expression of CD16 (lower in IS), CD115, and surface-associated NE (higher in IS). Neutrophil frequency and phenotype did not differ between IS and BAL. Finally, neutrophil frequency in IS correlated positively with air trapping. CONCLUSIONS: IS collected from 2-year-olds with CF yields biomarkers of early airway inflammation with good agreement with BAL, notably with regard to molecular and cellular outcomes related to neutrophils and monocytes/macrophages.

Administration of pilocarpine by microneedle patch as a novel method for cystic fibrosis sweat testing.

The sweat test is the gold standard for the diagnosis of cystic fibrosis (CF). The test utilizes iontophoresis to administer pilocarpine to the skin to induce sweating for measurement of chloride concentration in sweat. However, the sweat test procedure needs to be conducted in an accredited lab with dedicated instrumentation, and it can lead to inadequate sweat samples being collected in newborn babies and young children due to variable sweat production with pilocarpine iontophoresis. We tested the feasibility of using microneedle (MN) patches as an alternative to iontophoresis to administer pilocarpine to induce sweating. Pilocarpine-loaded MN patches were developed. Both MN patches and iontophoresis were applied on horses to induce sweating. The sweat was collected to compare the sweat volume and chloride concentration. The patches contained an array of 100 MNs measuring 600 µm long that were made of water-soluble materials encapsulating pilocarpine nitrate. When manually pressed to the skin, the MN patches delivered >0.5 mg/cm2 pilocarpine, which was double that administered by iontophoresis. When administered to horses, MN patches generated the same volume of sweat when normalized to drug dose and more sweat when normalized to skin area compared to iontophoresis using a commercial device. Moreover, both MN patches and iontophoresis generated sweat with comparable chloride concentration. These results suggest that administration of pilocarpine by MN patches may provide a simpler and more-accessible alternative to iontophoresis for performing a sweat test for the diagnosis of CF.

Bronchoscopic interventions for plastic bronchitis in children without structural heart disease.

Plastic bronchitis (PB) is a rare and life-threatening complication encountered in several disease states that leads to airway obstruction by branching casts. PB is most often reported in children with cyanotic congenital heart disease where recurrence is common, and mortality is high. There is limited data on optimal management strategies or recurrence of non-structural heart disease-related PB in children. We describe the clinical features, management, and outcomes in our cohort of children with non-structural heart disease-related PB. Among the 12 identified patients, asthma was the most common (67%) diagnosis. Ventilatory requirements ranged from room air to one patient who required extracorporeal membrane oxygenation (ECMO). Most patients (92%) required bronchoscopy, and cryotherapy was successfully utilized in two patients to relieve refractory obstructive airway casts. All patients received chest physiotherapy, and 11 patients were treated with two or more medications. There was one mortality despite ECMO, and one-third had recurrent PB, all of whom had asthma.Conclusion: Asthma is a risk factor for recurrent PB. Bronchoscopic interventions including cryotherapy are safe and effective treatment options in patients with refractory PB. What is Known: • Plastic bronchitis is a rare but life-threatening cause of airway obstruction caused by branching casts that are generally reported in patients with congenital heart disease. What is New: • In children without structural heart disease, asthma is a risk factor for recurrent plastic bronchitis. Cryotherapy via bronchoscopy is a safe and effective intervention in patients with refractory plastic bronchitis.

Variable phenotypes in congenital central hypoventilation syndrome with PHOX2B nonpolyalanine repeat mutations.

STUDY OBJECTIVES: Congenital central hypoventilation syndrome (CCHS) is a rare disorder affecting the autonomic nervous system that is caused by variants in the paired-like homeobox 2B (PHOX2B) gene. About 10% of patients with CCHS have nonpolyalanine repeat mutations (NPARM) that are associated with severe phenotypes requiring continuous assisted ventilation, Hirschsprung's disease, and increased neural crest tumor risk. However, some patients with NPARM have milder phenotypes. Our objective was to describe the phenotypes in patients with CCHS PHOX2B NPARM. METHODS: Retrospective case series of patients with CCHS PHOX2B NPARM was conducted at 2 children's hospitals to evaluate their phenotypes. RESULTS: We identified 8 patients with CCHS PHOX2B NPARM aged 3-31 years. Seven patients were diagnosed in infancy and 1 patient at 2 years of age. All patients presented with respiratory depression in the first 2 months of life. Only 1 patient was identified with a severe phenotype requiring continuous assisted ventilation, Hirschsprung's disease, and a neural crest tumor, which was resected. Five patients required positive pressure ventilation via tracheostomy only during sleep and 2 patients required oxygen only during sleep. Four patients had Hirschsprung's disease and 1 patient had a cardiac pacemaker due to a bradyarrhythmia. None of the patients had echocardiographic abnormalities. CONCLUSIONS: Patients with CCHS PHOX2B NPARM can have variable phenotypes, emphasizing the importance of implementing a plan of care that is individualized for each patient. The type of NPARM and their respective location on the PHOX2B gene may play a critical role in the severity of phenotypes displayed by each patient. CITATION: Kasi AS, Li H, Jurgensen TJ, Guglani L, Keens TG, Perez IA. Variable phenotypes in congenital central hypoventilation syndrome with PHOX2B nonpolyalanine repeat mutations. J Clin Sleep Med. 2021;17(10):2049-2055.

Elastase Exocytosis by Airway Neutrophils Is Associated with Early Lung Damage in Children with Cystic Fibrosis.

RATIONALE: Neutrophils are recruited to the airways of individuals with cystic fibrosis (CF). In adolescents and adults with CF, airway neutrophils actively exocytose the primary granule protease elastase (NE), whose extracellular activity correlates with lung damage. During childhood, free extracellular NE activity is measurable only in a subset of patients, and the exocytic function of airway neutrophils is unknown. OBJECTIVES: To measure NE exocytosis by airway neutrophils in relation to free extracellular NE activity and lung damage in children with CF. METHODS: We measured lung damage using chest computed tomography coupled with the Perth-Rotterdam Annotated Grid Morphometric Analysis for Cystic Fibrosis scoring system. Concomitantly, we phenotyped blood and BAL fluid leukocytes by flow and image cytometry, and measured free extracellular NE activity using spectrophotometric and Förster resonance energy transfer assays. Children with airway inflammation linked to aerodigestive disorder were enrolled as control subjects. MEASUREMENTS AND MAIN RESULTS: Children with CF but not disease control children harbored BAL fluid neutrophils with high exocytosis of primary granules, before the detection of bronchiectasis. This measure of NE exocytosis correlated with lung damage (R = 0.55; P = 0.0008), whereas the molecular measure of free extracellular NE activity did not. This discrepancy may be caused by the inhibition of extracellular NE by BAL fluid antiproteases and its binding to leukocytes. CONCLUSIONS: NE exocytosis by airway neutrophils occurs in all children with CF, and its cellular measure correlates with early lung damage. These findings implicate live airway neutrophils in early CF pathogenesis, which should instruct biomarker development and antiinflammatory therapy in children with CF.

Myeloperoxidase oxidation of methionine associates with early cystic fibrosis lung disease.

Cystic fibrosis (CF) lung disease progressively worsens from infancy to adulthood. Disease-driven changes in early CF airway fluid metabolites may identify therapeutic targets to curb progression.CF patients aged 12-38 months (n=24; three out of 24 later denoted as CF screen positive, inconclusive diagnosis) received chest computed tomography scans, scored by the Perth-Rotterdam Annotated Grid Morphometric Analysis for CF (PRAGMA-CF) method to quantify total lung disease (PRAGMA-%Dis) and components such as bronchiectasis (PRAGMA-%Bx). Small molecules in bronchoalveolar lavage fluid (BALF) were measured with high-resolution accurate-mass metabolomics. Myeloperoxidase (MPO) was quantified by ELISA and activity assays.Increased PRAGMA-%Dis was driven by bronchiectasis and correlated with airway neutrophils. PRAGMA-%Dis correlated with 104 metabolomic features (p<0.05, q<0.25). The most significant annotated feature was methionine sulfoxide (MetO), a product of methionine oxidation by MPO-derived oxidants. We confirmed the identity of MetO in BALF and used reference calibration to confirm correlation with PRAGMA-%Dis (Spearman's ρ=0.582, p=0.0029), extending to bronchiectasis (PRAGMA-%Bx; ρ=0.698, p=1.5×10-4), airway neutrophils (ρ=0.569, p=0.0046) and BALF MPO (ρ=0.803, p=3.9×10-6).BALF MetO associates with structural lung damage, airway neutrophils and MPO in early CF. Further studies are needed to establish whether methionine oxidation directly contributes to early CF lung disease and explore potential therapeutic targets indicated by these findings.

Serial Stimulated Jitter Analysis In Juvenile Myasthenia Gravis.

INTRODUCTION: Clinical and electrophysiological studies to measures disease activity in juvenile myasthenia gravis (JMG) are limited. METHODS: Retrospective review of the clinical profile, Myasthenia Gravis Foundation of America (MGFA) scores, serial stimulated jitter analysis (Stim-JA) of the orbicularis oculi muscle, grip strength, and spirometry of patients with JMG who were followed in a multidisciplinary clinic was performed. RESULTS: Thirteen patients with JMG (9 females) with mean age of 13.2 ± 4.8 years and follow-up duration of 25.3 ± 8.3 months (range, 6-39) with ≥ 2 Stim-JA recordings were included. The mean jitter, mean percentage of apparent single-fiber action potentials (%ASFAP) with increased jitter, and mean %ASFAP with blocking at baseline values (77.3 ± 54.7 µs, 64.3% ± 35.8%, 39% ± 38.6%, respectively) and at follow-up (53 ± 45.4 µs, 51.2% ± 34.5%, 17% ± 29.4%, respectively) were abnormal; however, no statistically significant interval difference was noted. The electrophysiological data correlated significantly with Myasthenia Gravis Foundation of America (MGFA) class. Grip strength and spirometry did not correlate with MGFA class. DISCUSSION: Stimulated jitter values are sensitive biomarkers in JMG. Muscle Nerve 58: 729-732, 2018.

Difference between SF6 and N2 multiple breath washout kinetics is due to N2 back diffusion and error in N2 offset.

Measurement of lung clearance index (LCI) by multiple breath washout (MBW) is a sensitive method for monitoring lung disease in patients with cystic fibrosis (CF). To compare nitrogen MBW (N2-MBW) and sulfur hexafluoride MBW (SF6-MBW), we connected these two gas analysis systems in series to obtain truly simultaneous measurements, with no differences other than the gas used. Nonsmoking healthy controls (HC) and subjects with CF were recruited at two institutions. The Exhalyzer-D (for N2-MBW measurement) was connected in series with the Innocor (for SF6-MBW measurement). Subjects washed in SF6 from a Douglas bag with tidal breathing and washed out SF6 and nitrogen with 100% oxygen provided as bias flow. Washout of both gases was continued past the LCI point (1/40th of equilibration concentration) in triplicate. N2-MBW resulted in higher cumulative exhaled volume, functional residual capacity (FRC), and LCI when compared with SF6-derived parameters in HC subjects (P < 0.0001 for all comparisons). All N2-MBW parameters were also significantly higher than SF6-MBW parameters in subjects with CF (P < 0.01 for all comparisons). After recalculation with a common FRC, N2-MBW LCI was higher than SF6-MBW LCI in subjects with CF (19.73 vs. 11.39; P < 0.0001) and in HC (8.12 vs. 6.78; P < 0.0001). Adjusting for N2 back diffusion and an offset error in the nitrogen measurement resulted in near complete agreement between the two methodologies. We found significant differences in LCI and FRC measurements using two different gases for MBW. This may have significant implications for the future use and interpretation of LCI data in clinical trials and routine clinical care.NEW & NOTEWORTHY This study provides important insights into the differences between the two techniques used for measuring lung clearance index (LCI): N2 and SF6 multiple breath washout. Differences between measurements made by these two methods in subjects with cystic fibrosis and healthy controls could be explained by nitrogen back diffusion and N2 offset error. This is important for use and interpretation of LCI data as an outcome measure for clinical trials and in routine clinical care.

COL6A and LAMA2 Mutation Congenital Muscular Dystrophy: A Clinical and Electrophysiological Study.

OBJECTIVES: COL6A and LAMA2 are subtypes of congenital muscular dystrophy. METHODS: Retrospective chart review of clinical findings, spirometry, muscle histology, muscle ultrasound, neuroimaging, and Electromyography (EMG)/Nerve Conduction Study data in genetically confirmed COL6A and LAMA2 subjects. RESULTS: We identified 8 COL6A and 6 LAMA2 subjects: the female-to-male ratio was 1.3:1 and the mean age was 11.9 ± 3.6 years. Gross motor delays since birth, proximal muscle weakness, and contractures were noted in both groups. Joint hyperlaxity and skin changes (follicular hyperkeratosis and muscle biopsy scar thinning) were unique to COL6A. Severe scoliosis, macrocephaly, and nonambulatory status were common in LAMA2. Increasing age was associated with poor respiratory function in COL6A. There was central "cloud appearance" on rectus femoris muscle ultrasound in COL6A and white matter T2 hyperintensity on brain magnetic resonance imaging in LAMA2. LAMA2 also showed demyelinating polyneuropathy. Neurogenic changes on EMG and muscle histology were noted in 37% and 33% of COL6A cases, respectively. CONCLUSIONS: COL6A has unique skin changes, central cloud appearance on muscle ultrasound. LAMA2 has demyelinating polyneuropathy and white matter changes on brain imaging. The presence of neurogenic changes on EMG and muscle histology in COL6A suggests motor axonal neuropathy. Genetic testing remains the gold standard in confirming COL6A congenital muscular dystrophy.

Risk Factors for Development of Pulmonary Hypertension in Infants with Bronchopulmonary Dysplasia: Systematic Review and Meta-Analysis.

OBJECTIVES: Preterm infants with bronchopulmonary dysplasia (BPD) are at increased risk for development of Pulmonary Hypertension (PHT). We performed a systematic review and meta-analysis to identify risk factors for development of PHT in infants with BPD. STUDY DESIGN: A systematic review identified risk factors for the development of PHT in infants with BPD. A meta-analysis of the pooled data was performed for each individual risk factor. RESULT: Of the 20 risk factors identified, 10 were repeated more than once in nine studies. Meta analysis showed that duration of mechanical ventilation, length of stay, oligohydramnios, use of high frequency ventilation, small for gestational age, sepsis and severity of BPD were significant risk factors; while birth weight and gestational age were inversely related. CONCLUSION: Several clinical variables are predictive of the development of PHT in infants with BPD. Prospective studies are needed to transform these risk factors into a risk-based scoring system.

A novel surfactant protein C gene mutation associated with progressive respiratory failure in infancy.

Mutations of the Surfactant Protein C (SPC) gene (SFTPC) have been associated with childhood interstitial lung disease (chILD) with variable age of onset, severity of lung disease, and outcomes. We report a novel mutation in SFTPC [c.435G->A, p.(Gln145)] that was associated with onset of symptoms in early infancy, progressive respiratory failure with need for prolonged mechanical ventilatory support, and eventual lung transplant at 1 year of age. While the mutation was not predicted to alter the amino acid sequence of the SP-C precursor protein, analysis of SP-C transcripts demonstrated skipping of exon 4. Because of limited data about the outcomes of infants with SFTPC mutations, we conducted a systematic review of all the SFTPC mutations reported in the literature in order to define their presenting features, clinical and radiologic features, and outcomes. Further advances in our understanding of chILD and creation of an international registry will help to track these patients and their outcomes. Pediatr Pulmonol. 2017;52:57-68. © 2016 Wiley Periodicals, Inc.