Overall long-term (>5 years) survival of subjects with two disease-causing ABCA3 mutations was <20%. Response to therapies needs to be ascertained in randomised controlled trials.

RATIONALE: Persistent tachypnea of infancy (PTI) is a specific clinical entity of undefined etiology comprising the two diseases neuroendocrine cell hyperplasia of infancy (NEHI) and pulmonary interstitial glycogenosis. The outcome of typical NEHI is favorable. The outcome may be different for patients without a typical NEHI presentation, and thus a lung biopsy to differentiate the diseases is indicated. OBJECTIVES: To determine whether infants with the characteristic clinical presentation and computed tomographic (CT) imaging of NEHI (referred to as "usual PTI") have long-term outcome and biopsy findings similar to those of infants with an aberrant presentation and/or with additional localized minor CT findings (referred to as "aberrant PTI"). METHODS: In a retrospective cohort study, 89 infants with PTI were diagnosed on the basis of clinical symptoms and, if available, CT scans and lung biopsies. Long-term outcome in childhood was measured on the basis of current status. MEASUREMENTS AND MAIN RESULTS: Infants with usual PTI had the same respiratory and overall outcomes during follow-up of up to 12 years (mean, 3.8 yr) as infants who had some additional localized minor findings (aberrant PTI) visualized on CT images. Both usual and aberrant PTI had a relatively favorable prognosis, with 50% of the subjects fully recovered by age 2.6 years. None of the infants died during the study period. This was independent of the presence or absence of histological examination. CONCLUSIONS: PTI can be diagnosed on the basis of typical history taking, clinical findings, and a high-quality CT scan. Further diagnostic measures, including lung biopsies, may be limited to rare, complicated cases, reducing the need for an invasive and potentially harmful procedure. AbstractRationale: Persistent tachypnea of infancy (PTI) is a specific clinical entity of undefined etiology comprising the two diseases neuroendocrine cell hyperplasia of infancy (NEHI) and pulmonary interstitial glycogenosis. The outcome of typical NEHI is favorable. The outcome may be different for patients without a typical NEHI presentation, and thus a lung biopsy to differentiate the diseases is indicated.

BackgroundAim of this study was to verify a systematic and practical categorization system that allows dynamic classification of pediatric DPLD irrespective of completeness of patient data.MethodsThe study was based on 2322 children submitted to the kids-lung-register between 1997 and 2012. Of these children 791 were assigned to 12 DPLD categories, more than 2/3 belonged to categories manifesting primarily in infancy. The work-flow of the pediatric DPLD categorization system included (i) the generation of a final working diagnosis, decision on the presence or absence of (ii) DPLD and (iii) a systemic or lung only condition, and (iv) the allocation to a category and subcategory. The validity and inter-observer dependency of this workflow was re-tested using a systematic sample of 100 cases.ResultsTwo blinded raters allocated more than 80 % of the re-categorized cases identically. Non-identical allocation was due to lack of appreciation of all available details, insufficient knowledge of the classification rules by the raters, incomplete patient data, and shortcomings of the classification system itself.ConclusionsThis study provides a suitable workflow and hand-on rules for the categorization of pediatric DPLD. Potential pitfalls were identified and a foundation was laid for the development of consensus-based, international categorization guidelines.Electronic supplementary materialThe online version of this article (doi:10.1186/s13023-015-0339-1) contains supplementary material, which is available to authorized users.

BackgroundLipids account for the majority of pulmonary surfactant, which is essential for normal breathing. We asked if interstitial lung diseases (ILD) in children may disrupt alveolar surfactant and give clues for disease categorization.MethodsComprehensive lipidomics profiles of broncho-alveolar lavage fluid were generated in 115 children by electrospray ionization tandem mass spectrometry (ESI-MS/MS). Two reference populations were compared to a broad range of children with ILD.ResultsClass and species composition in healthy children did not differ from that in children with ILD related to diffuse developmental disorders, chronic tachypnoe of infancy, ILD related to lung vessels and the heart, and ILD related to reactive lymphoid lesions. As groups, ILDs related to the alveolar surfactant region, ILD related to unclear respiratory distress syndrome in the mature neonate, or in part ILD related to growth abnormalities reflecting deficient alveolarisation, had significant alterations of some surfactant specific phospholipids. Additionally, lipids derived from inflammatory processes were identified and differentiated. In children with ABCA3-deficiency from two ILD causing mutations saturated and monounsaturated phosphatidylcholine species with 30 and 32 carbons and almost all phosphatidylglycerol species were severely reduced. In other alveolar disorders lipidomic profiles may be of less diagnostic value, but nevertheless may substantiate lack of significant involvement of mechanisms related to surfactant lipid metabolism.ConclusionsLipidomic profiling may identify specific forms of ILD in children with surfactant alterations and characterized the molecular species pattern likely to be transported by ABCA3 in vivo.

PIG is associated with alveolar growth abnormalities and has to be considered in all newborns with unexplained respiratory distress. Apparent treatment benefit of glucocorticosteroids needs to be evaluated systematically.

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RationaleABCA3 is a lipid transporter in the limiting membrane of lamellar bodies in alveolar type II cells. Mutations in the ABCA3 gene cause respiratory distress syndrome in new-borns and childhood interstitial lung disease. ABCA3 is N-terminally cleaved by an as yet unknown protease, a process believed to regulate ABCA3 activity.MethodsThe exact site where ABCA3 is cleaved was localized using mass spectrometry (MS). Proteases involved in ABCA3 processing were identified using small molecule inhibitors and siRNA mediated gene knockdown. Results were verified by in vitro digestion of a synthetic peptide substrate mimicking ABCA3’s cleavage region, followed by MS analysis.ResultsWe found that cleavage of ABCA3 occurs after Lys174 which is located in the proteins’ first luminal loop. Inhibition of cathepsin L and, to a lesser extent, cathepsin B resulted in attenuation of ABCA3 cleavage. Both enzymes showed activity against the ABCA3 peptide in vitro with cathepsin L being more active.ConclusionWe show here that, like some other proteins of the lysosomal membrane, ABCA3 is a substrate of cathepsin L. Therefore, cathepsin L may represent a potential target to therapeutically influence ABCA3 activity in ABCA3-associated lung disease.