Autoimmune interstitial lung disease

Autoimmune interstitial lung disease (ILD) refers to a group of lung disorders characterized by inflammation and scarring (fibrosis) of the interstitium, the tissue surrounding the lung’s air sacs, associated with autoimmune activity. Rather than being a single disease, autoimmune ILD can develop as a complication or manifestation of systemic autoimmune diseases, including rheumatoid arthritis, systemic sclerosis (scleroderma), and Sjögren disease.

Autoimmune-related ILD is commonly classified as connective tissue disease–associated interstitial lung disease (CTD-ILD). Some individuals with ILD exhibit autoimmune features without meeting the diagnostic criteria for a defined connective tissue disease. These cases may be classified as interstitial pneumonia with autoimmune features (IPAF), a research classification used to identify patients with suspected autoimmune involvement.

The disease can cause inflammation and progressive scarring of lung tissue, impairing breathing and oxygen exchange. Its severity and progression vary considerably depending on the underlying autoimmune condition, the pattern of lung involvement, and other individual factors.

Shortness of breath (especially during exertion), dry cough, fatigue, chest discomfort, and reduced exercise tolerance. In more advanced cases, patients may experience clubbing of the fingers or signs of low oxygen levels (cyanosis).

Autoimmune ILD is not classified as a primary autoimmune disease but can develop as a serious complication or manifestation of systemic autoimmune conditions. These include rheumatoid arthritis, systemic sclerosis (scleroderma), Sjögren disease, polymyositis, dermatomyositis, mixed connective tissue disease, and certain forms of systemic vasculitis, such as microscopic polyangiitis.

Risk factors include having a diagnosed autoimmune connective tissue disease, older age, a history of smoking, and certain genetic predispositions. The prevalence of ILD varies depending on the underlying autoimmune disease. For example, ILD affects approximately 10% of people with rheumatoid arthritis, but as many as 40–50% of those with systemic sclerosis. Environmental exposures, such as silica dust, may also contribute to increased risk in some individuals.

The progression and prognosis of autoimmune ILD vary depending on the underlying disease, the extent and pattern of lung involvement, and individual health factors. Some forms progress slowly, while others can cause rapid deterioration in lung function.

A 2026 study published in Clinical Rheumatology found that patients with connective tissue disease–associated ILD (CTD-ILD) or interstitial pneumonia with autoimmune features (IPAF) had more favorable survival outcomes than those with idiopathic forms of ILD. However, these findings were based on a retrospective, single-center study, and additional research is needed to determine how autoimmune disease classification influences long-term outcomes.

Early diagnosis, regular monitoring of lung function, and appropriate treatment are important for managing disease progression and reducing the risk of complications.