Covers diffuse parenchymal lung diseases, also called interstitial lung diseases, starting with their definition and a shared clinical picture, then the pathogenesis of inflammation versus fibrosis. It sets out a classification by cause, a table of HRCT patterns, lung function and BAL findings, and then idiopathic pulmonary fibrosis, the main other forms, and sarcoidosis, including the Löfgren and Heerfordt syndromes, a GRUELING mnemonic and Scadding staging. It closes with general treatment principles.
Topic 12 of 139 in the MU Sofia syllabus for Internal Diseases and Therapy (Medicine, Years 4 and 5). The free AceMed note covers it in 9 sections, about 1,579 words (13 min of reading), with 16 flashcards.
In this note
Definition
Pathogenesis
Classification
Clinical presentation
Diagnosis
Idiopathic pulmonary fibrosis (IPF)
Other important forms
Sarcoidosis
General principles of treatment of ILD
Definition
Diffuse parenchymal lung diseases (DPLD), also called interstitial lung diseases (ILD), are a heterogeneous group of over 200 disorders with varying degrees of inflammation and fibrosis of the lung parenchyma — mainly the interstitium (alveolar walls, septa), but also the alveolar spaces and small airways. They share a similar picture: exertional dyspnoea, dry cough, bilateral basal "velcro" crackles, diffuse infiltrates on imaging, a restrictive defect with reduced DLCO, and many progress to fibrosis, respiratory failure and cor pulmonale.
Pathogenesis
Repeated injury to the alveolar epithelium (type I pneumocytes) and capillary endothelium → increased alveolar permeability.
Either predominant inflammation (alveolitis: lymphocytes, macrophages, granulomas — often treatable) or aberrant repair: type II pneumocytes and growth factors (TGF-β, PDGF) activate fibroblasts → myofibroblasts → excessive collagen deposition → fibrosis.
Result: thickened, stiff interstitium → ↓ compliance and lung volumes (restriction), impaired diffusion and V/Q mismatch → hypoxaemia, first on exertion; destruction of the capillary bed → pulmonary hypertension; end stage: honeycomb lung.
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