Lipoid pneumonia: an overview.

Lipoid pneumonia is an uncommon disease caused by the presence of lipid in the alveoli. It is classified into two major groups, depending on whether the lipid/oil in the respiratory tract is from an exogenous (exogenous lipoid pneumonia) or endogenous/idiopathic (endogenous lipoid pneumonia) source. The usual presentation occurs with insidious onset and nonspecific respiratory symptoms such as dyspnea and/or cough. The main radiological findings include airspace consolidations, ground-glass attenuation, airspace nodules and 'crazy-paving' pattern. However, the radiological appearance of the disorder can mimic many other lung diseases, including carcinoma. Owing to the nonspecific clinical presentation and radiological features, the diagnosis is often missed or delayed. Pathologically, lipoid pneumonia is a chronic foreign body reaction to fat, characterized by lipid-laden macrophages. Diagnosis of this disease requires a high index of suspicion and can be confirmed by demonstration of lipid-laden macrophages in respiratory samples such as sputum, bronchoalveolar lavage fluid or fine-needle aspiration cytology/biopsy from lung lesions. Treatment protocols for this illness are poorly defined.