CME review Post Infectious Bronchiolitis Obliterans in Children Gilberto B. Fischer 1,2, *, Edgar E. Sarria 2,3 , Rita Mattiello 3,4 , Helena T. Mocelin 2 , Jose A. Castro-Rodriguez 5 1 Department of Paediatrics, Universidade Federal de Ciencias da Saude, Porto Alegre, Brazil 2 Pediatric Pulmonology Section, Hospital da Crianc ¸a Santo Antoˆnio, Porto Alegre, Brazil 3 Herman Wells Center for Pediatric Research, Indiana University, USA 4 Pediatric Post-Grad Program,Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil 5 Department of Paediatrics, School of Medicine, Pontificia Universidad Cato ´lica de Chile, Santiago, Chile INTRODUCTION Bronchiolitis Obliterans is a rare form of chronic obstructive lung disease secondary to a severe insult to the lower respiratory tract that leads to a variable degree of inflammation and scarring. The ultimate result of this process is the narrowing and/or complete obliteration of the small airways. 1 In children, the most common form is post-infectious bronchiolitis obliterans (PBO), except in locations with a considerable number of paediatric lung or bone marrow transplant recipients. As a disease, PBO has been reported in North and South America, Western and South-Eastern Europe, India, South-Korea, Taiwan, Malaysia, New Zealand, and Australia. In the last two decades of the 20 th century, South American countries accumu- lated an unexpected number of cases: more than seven hundred, according to the Bronchiolitis Obliterans in Latin America (BOLAT) initiative. This review covers important information on the epidemiology, risk factors, diagnosis, imaging, lung function, treatment and prognosis of PBO. EPIDEMIOLOGY There are reports of PBO secondary to influenza, parainfluenza, measles, respiratory syncytial virus, varicella, and Mycoplasma pneumoniae. However, adenovirus (Ad) is by far the most common agent linked to the development of PBO. 2–4 Thus, although the prevalence of PBO is not known, its epidemiology is directly related to the epidemiology of severe viral respiratory tract infections in Paediatric Respiratory Reviews 11 (2010) 233–239 EDUCATIONAL AIMS THE READER WILL BECOME FAMILIAR WITH:  The risk factors and epidemiology of post-infectious bronchiolitis obliterans (PBO)  The diagnostic criteria of PBO  The importance of imaging and pulmonary function testing in the diagnosis and follow-up of PBO  The multidisciplinary strategy for treating PBO  What is known about outcomes and prognosis of PBO ARTICLE INFO Keywords: Bronchiolitis obliterans child diagnosis respiratory function tests therapeutics tomography X-rays SUMMARY Bronchiolitis Obliterans (BO) is an infrequent chronic and obstructive lung disease secondary to an insult to the terminal airway and its surroundings. In children, the most common presentation is the post- infectious variant, closely related to a severe viral infection in the first three years of life. However, the increase in the number of lung and bone-marrow transplants has also been followed by an increase in post-transplant BO. Post-transplant BO is progressive while post-infectious BO does not seem to be, but both forms share some common pathways that result in a characteristic histopathology of bronchiolar obliteration. This review covers up-to-date evidence on epidemiology, diagnosis, treatment and prognosis of post-infectious bronchiolitis obliterans, including areas of controversy that need to be addressed in future studies. ß 2010 Published by Elsevier Ltd. * Corresponding author. Hospital da Crianc ¸a Santo Anto ˆnio, 58 andar, Servic ¸o de Pneumologia Pedia ´ trica, Av. Independe ˆncia, 155, Porto Alegre, Brazil 90035-074. Fax: +55 51 32148646. E-mail addresses: gbuenof@terra.com.br (G.B. Fischer), edgarsa01@hotmail.com (E.E. Sarria), rimattiello@hotmail.com (R. Mattiello), hmocelin@terra.com.br (H.T. Mocelin), jacastro17@hotmail.com (J.A. Castro-Rodriguez). Contents lists available at ScienceDirect Paediatric Respiratory Reviews 1526-0542/$ – see front matter ß 2010 Published by Elsevier Ltd. doi:10.1016/j.prrv.2010.07.005