Dangerous liaisons? Gastroesophageal reflux disease and organizing pneumonia.

nism is chronic recurrent subclinical microaspiration of gastric content or foreign particles into the lungs [2] . Although normal individuals aspirate small amounts of oral secretions during sleep [12] , a more prolonged aspiration can lead to the development of parenchymal lung disease. Gastric and bile acids have been shown to elicit an inflammatory response in the lung, and food particles per se, at a neutral pH, can also be the cause of lung inflammation leading to the accumulation of giant cells and the development of granulomas [3] . Although GERD does not necessarily lead to aspiration or microaspiration [13] , patients with advanced fibrotic lung diseases (IPF and pretransplant/scleroderma-associated fibrosis) have more often and more severe GERD [14, 15] . OP is characterized by a pathological pattern of patchy filling of the lung alveoli and respiratory bronchioles by loose plugs of granulation tissue. As a clinical entity, OP is associated with nonspecific symptoms of cough and dyspnea and radiographic findings of patchy alveolar infiltrates. OP may be associated with other underlying diseases (secondary OP) or it may be idiopathic (cryptogenic OP). Contrary to a fibrosing process such as in usual interstitial pneumonia/IPF, it responds strikingly well to corticosteroid therapy. On other occasions, OP may be just an incidental finding in lung biopsy specimens or In the last issue of Respiration , Gaillet et al. [1] report on the significance of gastroesophageal reflux disease (GERD) as a risk factor for the severity of organizing pneumonia (OP). In their series, patients with OP and GERD had more extensive radiological involvement, greater hypoxemia and greater bronchoalveolar lavage cellularity compared to those with OP in the absence of GERD. Moreover, relapses occurred more often in the group with than that without GERD. An association between GERD and lung diseases has long been suggested [2–4] . GERD is a well-recognized cause of posterior laryngitis and chronic cough [5, 6] , and a high prevalence of GERD has also been reported among patients with asthma [7] . In patients with lung fibrosis due to scleroderma, GERD is a common co-diagnosis and the severity of aspiration is associated with a worse prognosis [8] . Following lung transplantation, the aspiration of gastrointestinal contents has also been linked to a worse outcome and the development of bronchiolitis obliterans [9] . GERD is considered a risk factor for idiopathic pulmonary fibrosis (IPF). Animal studies, a prevalence of GERD reaching 94% in IPF patients [10] and a more favorable disease course after GERD treatment support this concept [11] . How does GERD contribute to the development of parenchymal lung disease? The main pathogenetic mechaPublished online: February 14, 2015