Pathogenesis and diagnostic work-up of patients with idiopathic pulmonary fibrosis
Among idiopathic interstitial pneumonias (IIP), idiopathic pulmonary fibrosis (IPF) is the most common form with an incidence of more than 10 cases per 100,000 population, increasing with age. The prognosis is poor and comparable to many malignant diseases. The time course is characterized by progressive dyspnoea and a decline of pulmonary function, often complicated by acute exacerbations or the development of pulmonary hypertension. IPF is considered to be a result of an abnormal alveolar wound repair process after repeated epithelial microinjuries by so far unknown agents, rather than a primary inflammatory disorder. The diagnosis is based on clinical symptoms and findings like crackles over the basal areas of the lung, impairment of pulmonary function (restriction, reduced diffusion capacity, hypoxemia), and the absence of an alternative diagnosis. High resolution computed tomography (HRCT) has been established as a powerful tool that allows the diagnosis of IPF in experienced centres without the performance of a surgical lung biopsy. The characteristic histopathological pattern is usual interstitial pneumonia (UIP) showing a typical heterogenous pattern and fibroblast foci. Faced with a poor prognosis and the lack of an effective treatment, it is very important to distinguish IPF from other interstitial lung diseases like other IIP (in particular non-specific interstitial pneumonia NSIP), drug-induced pulmonary fibrosis, asbestosis, extrinsic allergic alveolitis, sarcoidosis or diffuse parenchymal lung diseases associated with connective tissue diseases. Currently, no effective therapy is available and anti-inflammatory treatment is of limited value. However, new insights into the pathogenesis of IPF opened up novel therapeutic options, which are currently investigated in clinical trials.