The lung and the gut: Common origins, close links Donata Girosi, Simona Bellodi, Federica Sabatini and Giovanni A. Rossi * Pulmonary and Allergy Units, G. Gaslini University Hospital, Genoa, Italy INTRODUCTION The gastrointestinal tract and the respiratory tract recog- nize a common embryologic origin, both enter significant functional changes immediately after birth, and represent the largest immunologic organs in the body, possessing the greatest surface area exposed to the outside environment. This is confronted with the largest antigenic load in the form of inhaled organic and inorganic particles (the lung) and of dietary proteins (the gut), commensal organisms (the gut), and pathogens (the lung and the gut). 1 Because of the common embryologic origin, alteration of the many factors modulating the development often results in structural abnormalities involving the two sys- tems. 2 Despite the several structural similarities, the immune reaction to antigenic exposure shows significant diversities: in contrast with mucosal immune system of the lung, which strongly reacts to all inhaled organic and inorganic particles and organisms, the mucosal immune system of the gut has the extraordinary ability to distinguish between foreign pathogens and safe nutrient proteins and commensal organisms. 3 However, in few instances in which these responses go wrong, individuals might experience food hypersensitivity or inflammatory bowel disorders that may also cause airway or lung manifestations. 3,4 In this review we will only briefly outline some of the most common disorders of the airways linked to common PAEDIATRIC RESPIRATORY REVIEWS (2006) 7S, S235–S239 KEYWORDS bronchopulmonary- foregut malformations; congenital cystic adenomatoid malformation of the lung; pulmonary sequestration; congenital pulmonary lobar emphysema; bronchogenic cyst; growth factors; regulatory peptides Summary Because of the common embryologic origin, alteration of the many factors modulating the development of the alimentary and the respiratory tract often results in structural abnormalities involving the two systems. Indeed, some of the most common embryologic disorders of the airways are frequently associated with anomalies of the gastrointestinal tract. Lung growth occurs as a series of tightly regulated events, depending on a number of factors, including developmental, genetic and environment ones. Abnormalities of any of these factors may causes developmental alterations of the lung leading to a group of disorders termed ‘‘bronchopulmonary-foregut malformations’’. These are usually sporadic, solitary cystic hamartomas, involving conducting airways, arteries, venous drainage, and lung parenchyma, which are now often discovered on routine prenatal sonography. While some lesions may be large and cause serious complications in the foetus or newborn, many will be asymptomatic at birth, raising controversy about management: simple observation or surgery and, if so, at what age? Over the past two decades molecular studies have started to shed light on the complex series of events that control proper formation of the lung, with the hope that a better understanding of the molecular basis of pulmonary maturation will allow the design of new therapeutic strategies. ß 2006 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +39 10 5636/547; fax: +39 10 383953. E-mail address: giovannirossi@ospedale-gaslini.ge.it (G.A. Rossi). 1526-0542/$ – see front matter ß 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.prrv.2006.04.192