Vasculitis is a group of rare autoimmune diseases defined by inflammation within the walls of blood vessels throughout the body. This inflammation causes vessel walls to thicken, narrow, or scar, restricting blood flow and potentially leading to organ and tissue damage. When this process affects the vessels of the lungs, it is specifically referred to as pulmonary vasculitis. The long-term outlook is highly dependent on the speed of diagnosis and the effectiveness of immediate treatment.
Understanding Pulmonary Vasculitis
The mechanism involves the immune system mistakenly attacking the body’s own blood vessel cells, triggering an inflammatory cascade. This inflammation primarily targets the small-to-medium-sized vessels within the lung tissue. One of the most immediate consequences is pulmonary capillaritis, which involves inflammation of the tiny capillaries surrounding the air sacs.
Capillaritis can lead to diffuse alveolar hemorrhage (DAH), where the capillaries rupture and cause bleeding into the alveoli. This bleeding impairs the lung’s ability to exchange oxygen and carbon dioxide, often leading to respiratory distress or failure. Patients frequently present with shortness of breath, a persistent cough, and hemoptysis (coughing up blood). Over time, chronic inflammation can also lead to scarring, or fibrosis, in the lung tissue, permanently reducing lung capacity.
Major Forms of Lung-Affecting Vasculitis
Pulmonary vasculitis is a manifestation of several systemic conditions, most commonly categorized as Antineutrophil Cytoplasmic Antibody-Associated Vasculitides (AAVs). The specific type of AAV largely dictates the pattern of organ involvement and the prognosis. These diseases are linked by the presence of autoantibodies, known as ANCA, which target proteins within white blood cells.
Granulomatosis with Polyangiitis (GPA) is one of the most common forms and frequently involves the lungs, upper respiratory tract, and kidneys. A defining feature of GPA is necrotizing granulomatous inflammation, which can cause lung nodules and cavitating lesions.
Microscopic Polyangiitis (MPA) primarily affects the small vessels and is strongly associated with diffuse alveolar hemorrhage and rapidly progressive kidney failure. MPA typically lacks the granulomas seen in GPA and is often associated with a different type of ANCA.
Eosinophilic Granulomatosis with Polyangiitis (EGPA) is characterized by asthma, a high count of eosinophils, and necrotizing vasculitis. While it can cause lung nodules, it is less likely to cause the severe alveolar hemorrhage seen in GPA or MPA. Mortality in EGPA is often linked to cardiac complications.
Treatment Strategies and Disease Management
The management of pulmonary vasculitis aims at quickly controlling inflammation and achieving disease remission. Treatment is typically divided into two phases: an initial, intensive induction phase followed by a long-term maintenance phase.
Induction therapy for severe disease involves high-dose glucocorticoids combined with powerful immunosuppressive agents. The primary immunosuppressants used include cyclophosphamide or the biologic agent rituximab. Cyclophosphamide is a chemotherapy drug that suppresses the immune system, while rituximab is a monoclonal antibody that targets B-cells. Both are highly effective in rapidly controlling active vasculitis and preventing further organ damage.
Once the disease is in remission, the patient transitions to maintenance therapy, which uses lower doses of immunosuppressive drugs to prevent relapse. Medications often used include azathioprine, methotrexate, or mycophenolate mofetil, sometimes rotated with periodic rituximab infusions. Maintenance therapy is typically continued for 24 to 48 months, or longer if the patient is at high risk for relapse. Supportive care, such as oxygen therapy for lung damage or plasma exchange for rapidly progressive organ failure, is also a component of management.
Prognosis and Factors Influencing Life Expectancy
The life expectancy for pulmonary vasculitis has been transformed since the introduction of modern immunosuppressive treatments. Prior to these therapies, the prognosis was poor, with median survival being only a few months. Today, the outlook is significantly improved, with high rates of remission achievable for most patients.
Long-term survival is influenced by several factors, including the severity of the disease at diagnosis and the extent of initial organ damage. Involvement of organs like the kidneys or the heart, which can occur alongside lung involvement, worsens the overall prognosis. Patients with ANCA antibodies targeting proteinase 3 (PR3-ANCA) tend to have a higher risk of relapse compared to those with MPO-ANCA.
The patient’s response to the initial induction therapy is also a strong predictor of long-term outcome. While life expectancy is better, the risk of death remains higher than in the general population, particularly in the first year due to active disease or treatment-related infections. Even after remission, long-term organ damage, such as lung scarring or chronic kidney disease, can affect quality of life and modify lifespan.