PulmonaryMatthias Griese, MD Alveolar Proteinosis: A abstract Comprehensive’ Clinical Perspective Pulmonary alveolar proteinosis is a broad group of rare diseases that are defined by the occupation of a lung s gas-exchange area by pulmonary surfactants that are not properly removed. The clinical and radiologic phenotypes among them are very similar. The age of manifestation plays a central role in the differential diagnosis of the almost 100 conditions and provides an efficient path to the correct diagnosis. The diagnostic approach is tailored to identify genetic or autoimmune causes, exposure to environmental agents, and associations with numerous other diseases. Whole-lung lavages are the cornerstone of treatment, and children in particular depend on the expertise to perform such therapeutic lavages. Other treatment options and long-term survival are related to the condition causing the proteinosis. 3 Under pathological conditions, the inhabitants4 . The first description of alveolar airspaces can be filled with PAP as well as the vast majority of various materials, which frequently data on treatment and prognosis are replace the air necessary for gas related to autoimmune PAP. Most Department of Pediatric Pneumology, Dr von Hauner exchange and give rise to alveolar pediatric cases are nonautoimmune Children’s Hospital, Ludwig-Maximilians-University of Munich and the German Center for Lung Research, Munich, filling syndromes (‍Table 1). These PAP and distribute almost evenly Germany conditions have similar clinical and among many different entities. In radiologic presentations. This makes childhood, there is a bimodal age DOI: https:// doi. org/ 10. 1542/ peds. 2017- 0610 their differential diagnosis difficult. distribution; some conditions manifest Accepted for publication Apr 11, 2017 in the neonatal period (‍Fig 2, upper Address correspondence to Matthias Griese, MD, Pulmonary alveolar proteinosis (‍PAP) portion), whereas others manifest Dr von Hauner Children’s Hospital, University of is defined by the accumulation of during infancy and childhood. Munich, Lindwurmstr 4, 80337 München, Germany. pulmonary surfactants in the alveolar E-mail: [email protected] space (‍Fig 1). Mechanistically, these PATHOLOGY PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, disturbances of surfactant homeostasis 1098-4275). Copyright 2017 by the American Academy of may be caused by an altered surfactant1 © production, removal, or both. PAP is The expansion of the surfactant pool Pediatrics can be recognized in histopathological FINANCIAL DISCLOSURE: The author has indicated a heterogeneous group of disorders 2 that is caused by different conditions specimens. The alveoli are filled with he has no financial relationships relevant to this (‍Table 2). The age of manifestation eosinophilic, acellular, and finely article to disclose. plays an important role in the granular material (‍Fig 1E). Clefts FUNDING: Funded by the German Center for Lung Research, DZL 2.0, the European Management diagnostic approach and differential made4, 5 of cholesterol can be found (‍Fig Platform for Children s Interstitial Lung Disease 1F). Sometimes, detached type II ’ diagnosis (‍Fig 2). Success of treatment (FP7, 305653), and E-Rare 2016. and outcome are related to the pneumocytes, foamy macrophages, or neutrophil granulocytes as well as POTENTIAL CONFLICT OF INTEREST: The author has underlying condition and, in children, to indicated he has no potential conflicts of interest the technical skills needed to perform lamellar bodies of normal lungs can be to disclose. whole-lung lavages (‍WLLs). WLL is the identified (‍Fig 1 C and D). cornerstone of PAP treatment. EPIDEMIOLOGY Whereas the intra-alveolar filling does To cite: Griese M. Pulmonary Alveolar Proteinosis: not differentiate between different A Comprehensive Clinical Perspective. Pediatrics. forms of PAP, histopathological 2017;140(2):e20170610 PAP is a rare disease complex examination of the alveolar wall that affects <5 cases per 100000 structures may be normal (‍Fig 1E) Downloaded from www.aappublications.org/news by guest on October 1, 2021 PEDIATRICS Volume 140, number 2, August 2017:e20170610 STATE-OF-THE-ART REVIEW ARTICLE or abnormal. The interstitial space idiopathic pulmonary hypertension occurs in children, and it needs is mostly normal; however, several in a mature neonate. to be differentiated from GM-CSF forms show4, 6widening from cells INVESTIGATIONS AND DIFFERENTIAL antibodies in healthy individuals or fibrosis. When the surfactant DIAGNOSIS at low levels and patients with “ dysfunction syndromes were first autoinflammatory diseases such as ” Chest Radiography – 21 described, the term congenital colitis, Crohn disease, malignancies,22 24 alveolar proteinosis7 was used or PAP caused by dust exposure. in such newborns. Particularly Because there is a close correlation in children, the PAP histopattern The presence of diffuse bilateral between antibody level and PAP mostly symmetrical alveolar, 25, 26 presents in combination 8,with 9 development, a close link additional histopatterns, such sometimes patchy infiltrates with to pulmonary manifestation is as increased cellularity from air bronchograms give first clues mandatory when searching for these to interstitial lung disease due to hyperplasia of type II pneumocytes Lactateautoantibodies. Dehydrogenase and collagen fibers or alveolar alveolar filling (‍Fig 1A). Usually, ∼ 10 macrophages. In cohort studies in the perimediastinal regions are 50% to 60% of such biopsies, the more affected than the subpleural 11, 12 Lactate dehydrogenase is increased PAP histopattern was found, regions. Persistence of the cloudy in 82% of patients with autoimmune and the detection rate was higher in infiltrates after antibiotic treatment 6 is a frequent observation. In neonates PAP. Of interest, this marker biopsies conducted during the early “ ” 12 readily responds to changes in disease phase. In TTF1 deficiency, with acute RDS, all radiologic stages – disease severity and improves after pulmonary histology may also show (‍including a white lung ) may 6,27 29 develop progressively. therapeutic lavages. the PAP pattern in addition to the Lung Function Tests nonspecific interstitial pneumonia Similarly, in serum carcinoembryonic antigen, levels of the surfactant pattern and defects13 in lung 30 proteins A, D, and KL-6 are markers development. Adults and children who are old of disease activity, which can be CLINICAL PRESENTATION enough to perform spirometry have used to monitor its course. Serum a restrictive pattern with small KL-6 accurately predicts disease lung volumes and reduced diffusing 29 – progression in autoimmune PAP. PAP presents in 2 types: Most capacity of the lung for carbon frequently (‍70% 90% of PAP cases), monoxide, although 6initial tests In children and adults, autoantibodies patients develop slowly increasing may also be normal. Of interest, including antinuclear antibody, dyspnea (‍initially2 on exertion) and carbon dioxide elimination rarely is antineutrophil cytoplasmic antibody – dry coughing. In PAP caused by a problem in the face of significant (‍eg, cANCA/PR3 and pANCA/ granulocyte-macrophage colony- hypoxemia. At presentation, 55% MPO), anti double-stranded DNA, stimulating factor receptor alpha of the patients with PAP caused anticentromere, cyclic citrullinated – – (‍GM-CSF-Ra) mutations, 70% had by GM-CSF-Ra mutations had peptide, extractable nuclear antigen 14 – dyspnea at presentation, 15% had hypoxemia, whereas in adults with (‍eg, anti SS-A [Ro], anti SS-B [La], tachypnea, 30% had clubbing, 35% autoimmune PAP, hypoxemia at anti-RNP, anti Jo-1, anti-Sm, and Scl- had global respiratory failure, and 14 rest was present in approximately 70), and rheumatoid factor should be 15% were intubated and ventilated. – one-third and during exercise 3in assessed. more than half of the patients. With Global and specific immunologic Less frequently (‍30% 50% of PAP treatment of the alveolar filling, function tests need to be done cases), fever, weight loss, fatigue, abnormal lung function tests are to diagnose underlying immune and chest pain are observed expected to be reversible; if they are Geneticdeficiencies Testing (‍Table 2). (‍numbers2 are for autoimmune not, then additional pathology should PAP ). Among the children, 45% had Laboratorybe suspected. Blood Tests infections (‍mycoplasma, influenza, or respiratory syncytial virus) Autoantibodies Against GM-CSF In neonates with the characteristic before PAP because of GM-CSF-Ra clinical and radiologic presentation mutations, 26% had a cough, 5% (‍and after the exclusion of other, had a fever,14 and 36% had failure In all cases of suspected PAP, these– more frequent causes), testing for to thrive. PAP caused by affected should be searched. In adults, >90%15 19 mutations in SFTPB, SFTPC, ABCA3, surfactant production typically of the case results are positive. and TTF1 is recommended (‍www. presents with idiopathic respiratory Serology has excellent20 sensitivity childeu. net). In infants and older distress syndrome (‍RDS) or and specificity. Autoimmune PAP patients, analysis for mutations in Downloaded from www.aappublications.org/news by guest on October 1, 2021 2 GRIESE TABLE 1 Intra-Alveolar Filling With Different Materials Leads to Various Disease Entities Material Filling the Alveolar Space Disease excluding cardiac, infectious, central, Surfactant PAP or metabolic causes). In older infants Erythrocytes, siderophages Alveolar hemorrhage Macrophages Desquamative