Pathophysiology
Summary
In the context of interstitial lung diseases, such as idiopathic pulmonary fibrosis (IPF) and cryptogenic organizing pneumonia (COP), restrictive lung disease is a common outcome, often involving a component of pulmonary fibrosis. Idiopathic pulmonary fibrosis (IPF) serves as the prototypical fibrosing disorder leading to restrictive lung disease. IPF is linked to recurrent cycles of alveolitis of unknown origin, damaging both type 1 and type 2 alveolar cells in the alveolar epithelium. This initiates a cascade where damaged type-1 pneumocytes release cytokines like TGF-beta-1, activating fibroblasts and ultimately leading to pulmonary fibrosis. Histologically, IPF presents with patchy fibrosis, known as usual interstitial pneumonia (UIP), and a characteristic ‘cobblestone' appearance of the pleural surface due to retraction scars along the interlobular septa. Radiological findings often reveal bilateral or diffuse reticular opacities, predominantly in the lower lobes. These opacities tend to distribute along sub-pleural regions and interlobular septa. The phenomenon of alveoli collapse and dilated proximal airways in IPF manifests as a honeycombing pattern on CT and gross pathology.
Besides IPF, other conditions like cryptogenic organizing pneumonia (COP), also known as bronchiolitis obliterans organizing pneumonia (BOOP), can cause pulmonary fibrosis. COP generally manifests with acute onset of cough, dyspnea, fever, and weight loss, and is effectively treated with oral corticosteroids. Several medications like amiodarone, bleomycin, and methotrexate can also induce pulmonary fibrosis. Additionally, patients with a history of thoracic radiation can develop radiation pneumonitis, which may present with pleural effusion and is also treatable with oral corticosteroids. Autoimmune conditions like lupus, systemic sclerosis, and rheumatoid arthritis can also lead to pulmonary fibrosis.
Lesson Outline
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FAQs
Idiopathic pulmonary fibrosis (IPF) is a specific form of chronic, progressive fibrosing interstitial lung disease of unknown cause. It is the prototypical fibrosing disorder, and is one of many interstitial lung diseases characterized by thickening and fibrotic scarring of the lung tissue. This scarring impairs lung function and hampers the efficient transfer of oxygen into the bloodstream.
While the etiology of IPF is unknown, the pathological process is likely related to cyclical lung injury from recurrent episodes of alveolitis. This inflammation repetitively damages both type 1 and type 2 alveolar cells in the alveolar epithelium. The damaged type-1 pneumocytes release cytokines like TGF-beta-1, which activate fibroblasts, leading to pulmonary fibrosis. Histologically, this manifests as patchy fibrosis, often referred to as usual interstitial pneumonia (uip).
Radiological imaging of IPF often reveals bilateral or diffuse reticular opacities that are most prominent in the lower lobes. These opacities tend to align along the sub-pleural regions and interlobular septa, giving the pleural surface a ‘cobblestone’ appearance. Additionally, the collapse of alveoli and dilation of proximal airways can manifest as a honeycombing pattern on CT scans.
Pulmonary fibrosis can be caused by a variety of conditions and triggers, including cryptogenic organizing pneumonia (cop), also known as bronchiolitis obliterans organizing pneumonia (boop), as well as exposure to certain medications like amiodarone, bleomycin, and methotrexate. Additionally, thoracic radiation can lead to radiation pneumonitis and subsequent pulmonary fibrosis. Collagen vascular diseases such as lupus, systemic sclerosis, and rheumatoid arthritis can also be culprits.
Cryptogenic organizing pneumonia typically presents with an acute onset of symptoms including cough, dyspnea, fever, and weight loss. In many cases, cop responds well to treatment with oral corticosteroids.
