Question

Discuss the pathogenesis of connective tissue disease-associated interstitial lung disease (CTD-IL.

Hint:

The pathogenesis of CTD-ILD is driven by immune-mediated inflammation and fibrosis, which leads to progressive lung function impairment.

Answer 1

Step 1: Overview of CTD-ILD.
Connective tissue disease-associated interstitial lung disease (CTD-ILD) is a term used to describe interstitial lung disease (ILD) occurring as a complication of systemic autoimmune diseases, including rheumatoid arthritis, systemic sclerosis (scleroderm, systemic lupus erythematosus (SLE), and polymyositis.
Step 2: Immunological Mechanisms.
The pathogenesis of CTD-ILD involves an immune-mediated process where autoantibodies and immune cells attack the lung interstitium, leading to inflammation and fibrosis. In systemic sclerosis (scleroderm, for example, excessive collagen production and fibrosis occur due to the activation of fibroblasts and the production of profibrotic cytokines, such as transforming growth factor-beta (TGF-β).
Step 3: Fibrosis and Lung Remodeling.
Chronic inflammation and fibrosis in the lung interstitium lead to decreased lung compliance, impaired gas exchange, and reduced lung volume. Over time, these changes result in symptoms such as dyspnea (difficulty breathing), dry cough, and reduced exercise tolerance.
Step 4: Clinical Manifestations and Progression.
CTD-ILD can progress gradually, and some forms of ILD associated with systemic sclerosis or rheumatoid arthritis may present with acute exacerbations. Early diagnosis and treatment are essential to reduce fibrosis and prevent irreversible lung damage.