Diffuse parenchymal lung disease

The diffuse parenchymal lung diseases (DPLDs) are a group of over 200 diverse conditions all of which effect either the alveolar space or the pulmonary interstitium. The DPLDs typically present with dyspnoea and diffuse infiltrates on chest X-ray. Achieving an exact diagnosis is frequently challenging and relies upon careful history-taking and detailed examination, integrated with the results of appropriate investigations. Key amongst these investigations is high-resolution computed tomography (HRCT) scanning. The recognition that many of the DPLDs have distinctive HRCT appearances has greatly reduced the need for biopsy in many of these conditions. Of the DPLDs, the most frequently encountered in clinical practice are the idiopathic interstitial pneumonias, a group of diseases of unknown aetiology and including idiopathic pulmonary fibrosis and cryptogenic organizing pneumonia. Despite recent developments in understanding of the pathogenesis of fibrotic lung disease it remains the case that many of the DPLDs are poorly responsive to therapy. Novel treatments have been developed over the last decade and it is to be hoped that these will improve outcomes for patients with parenchymal lung disease. This chapter covers the key aspects to be considered in the history, examination and investigation of patients with suspected DPLD. Also covered is the classification of the idiopathic interstitial pneumonias with particular attention paid to their pathogenesis, diagnosis and management. A brief summary is also provided of some of the rarer DPLDs.