Acute exacerbations of interstitial lung disease

Interstitial lung diseases (ILDs), or diffuse parenchymal lung disorders, constitute a group of more than 150 different disorders characterised by inflammation of the lung parenchyma or interstitium, sometimes followed by the occurrence of pulmonary fibrosis. In the most frequently occurring interstitial disorders, such as sarcoidosis, idiopathic pulmonary fibrosis (IPF), idiopathic nonspecific interstitial pneumonia, hypersensitivity pneumonitis and collagen vascular disease-related interstitial pneumonias, acute worsening of pulmonary symptoms can occur that can be defined as an acute exacerbation. There are important differences in presentation, aetiology and prognosis of acute exacerbations between these different ILDs. In sarcoidosis, an acute exacerbation is defined as an increase of pulmonary symptoms caused by new or worsening granulomatous inflammation. In acute exacerbations of IPF, for example, an acute worsening has to be present with new ground-glass abnormalities on CT and can be provoked by multiple triggers, such as infection, mechanical ventilation, drug toxicity and aspiration. When an acute exacerbation occurs in sarcoidosis, starting or increasing the dose of prednisolone is often successful. Steroids are also often used in treating an acute exacerbation of IPF, although unfortunately with a much lower chance of success. In acute exacerbations of non-IPF pulmonary fibrosis there might be an even more logical rationale for increasing the amount of immune suppression. However, in line with IPF, strong evidence is also lacking, indicating the need for future studies addressing this issue. Best supportive care during acute exacerbations, such as mechanical ventilation, is challenging and should be discussed case by case.