Organizing Pneumonias

Lazor, Romain

Organizing pneumonia is a particular type of inflammatory and reparative reaction of the lung parenchyma characterized by fibroblast proliferation in the distal airspaces with overall preservation of the lung architecture. When microscopic, it is an asymptomatic and nonspecific reaction of little clinical significance accompanying many pathological processes. When macroscopic and affecting large portions of the lung parenchyma, it manifests by restrictive ventilatory defect and gas exchange impairment leading to dyspnea, cough, hypoxemia, alveolar opacities at chest imaging, and symptoms of systemic inflammation such as fever, malaise, and weight loss. This picture constitutes the clinico-pathological syndrome of organizing pneumonia, which has been recognized and characterized as a distinct entity in the past 30 years. Although the classical features of organizing pneumonia are increasingly familiar to chest physicians, and the efficacy of corticosteroid treatment makes it appear at first sight as an easy problem to resolve, atypical clinical presentations, similarities with other diseases, severe forms, histological variants, side effects of therapy, and relapses can make the management more difficult than initially expected. This chapter will address the classical and less common features of organizing pneumonia, and will provide practical clues to the diagnosis and management of this disorder.