Most forms of vasculitis are autoimmune diseases, meaning the immune system mistakenly attacks blood vessel walls. However, vasculitis is not a single condition. It is a group of over 20 disorders, and while the majority involve autoimmune mechanisms, some are driven by different parts of the immune system or triggered by external factors like infections and medications.
Why Most Vasculitis Is Autoimmune
In autoimmune disease, the body produces antibodies or immune cells that target its own tissues. This is exactly what happens in many forms of vasculitis. The clearest example is a group called ANCA-associated vasculitis, where the immune system generates specific antibodies (called antineutrophil cytoplasmic antibodies) that attack white blood cells. Those white blood cells then damage the walls of small blood vessels throughout the body. A blood test can detect these antibodies and help identify which subtype of vasculitis is present.
Other forms involve immune complexes, clusters of antibodies and proteins that deposit in vessel walls and trigger inflammation. IgA vasculitis (formerly called Henoch-Schönlein purpura) works this way, as does cryoglobulinemic vasculitis. In both cases, the immune system is generating a misguided attack on the body’s own blood vessels.
The Exceptions: Not All Vasculitis Is Autoimmune
A few forms of vasculitis are better described as autoinflammatory rather than autoimmune. The difference is technical but meaningful. Autoimmune diseases involve the adaptive immune system, the part that creates targeted antibodies and specialized immune cells. Autoinflammatory diseases instead involve the innate immune system, a more primitive defense that triggers inflammation broadly, without producing specific antibodies.
Behçet’s disease is the most notable example. It causes vasculitis affecting vessels of all sizes, but researchers have found no autoimmune T or B cells driving the process. Its episodic flares and pattern of inflammation resemble autoinflammatory conditions more closely. So while it causes real blood vessel damage, the underlying mechanism is distinct from the antibody-driven forms.
Vasculitis can also be secondary, triggered by something outside the immune system itself. Hepatitis B and hepatitis C infections can cause vasculitis. Certain drugs, including cocaine, hydralazine, and propylthiouracil, are among the most common medication triggers. Antibiotics like quinolones, NSAIDs, and even some cancer therapies have been linked to drug-induced vasculitis affecting skin, brain, or large blood vessels. In these cases, the vasculitis is a reaction rather than a primary autoimmune disorder, and it often improves when the trigger is removed.
Types of Vasculitis by Vessel Size
Vasculitis is classified by the size of blood vessels it primarily affects. This system, established by an international consensus conference, shapes how the disease is diagnosed and treated.
- Large vessel vasculitis targets the aorta and its major branches. The two main types are giant cell arteritis and Takayasu arteritis. Giant cell arteritis typically strikes adults over 50, causing new headaches (often in the temples), scalp tenderness, fever, fatigue, and weight loss. About two-thirds of patients develop headache as a hallmark symptom.
- Medium vessel vasculitis affects the main arteries supplying organs. Polyarteritis nodosa is the primary adult form, and Kawasaki disease affects children. Polyarteritis nodosa is particularly aggressive: neurological problems like nerve damage occur in roughly 70% of patients, skin involvement in 25 to 60%, gastrointestinal symptoms in 40 to 60%, and kidney disease in about 40%.
- Small vessel vasculitis damages capillaries, venules, and small arteries. This category includes the ANCA-associated types (granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis) as well as the immune complex types like IgA vasculitis. IgA vasculitis causes a visible skin rash (palpable purpura) in nearly all patients, joint pain in 60 to 70%, and kidney involvement in up to 70% of adults.
Common Symptoms Across Types
Because vasculitis can affect blood vessels anywhere in the body, symptoms vary widely depending on which organs lose blood supply. That said, most forms share a set of constitutional symptoms: fever, fatigue, unintentional weight loss, and a general feeling of being unwell. These symptoms alone are vague, which is one reason vasculitis is notoriously difficult to diagnose.
The more telling signs depend on which organs are involved. Skin changes like purplish spots, tender nodules, or ulcers are common. Kidney damage can show up silently in blood and urine tests before causing noticeable symptoms. Lung involvement may cause coughing or shortness of breath. Nerve damage can produce numbness, tingling, or weakness in the hands and feet. When vasculitis is suspected, biopsies of the skin, kidney, upper airways, muscles, or lungs are the most common ways to confirm the diagnosis.
How Vasculitis Is Treated
Treatment for vasculitis centers on suppressing the immune system’s attack on blood vessels. For severe or organ-threatening disease, treatment typically starts with high-dose steroids combined with a stronger immune-suppressing therapy. The two primary options for that initial phase are rituximab, a biologic drug that depletes the B cells responsible for producing harmful antibodies, and cyclophosphamide, an older but effective immunosuppressant. Rituximab is FDA-approved specifically for granulomatosis with polyangiitis and microscopic polyangiitis in adults.
The steroid dose is reduced on a defined schedule, with the goal of reaching a low dose within four to five months. This matters because long-term high-dose steroids carry significant side effects, including bone thinning, weight gain, high blood sugar, and increased infection risk. Once the disease is under control (a phase called remission), patients typically stay on a lower-intensity maintenance therapy to prevent relapse. Options for maintenance include rituximab, methotrexate, or azathioprine.
For milder, non-organ-threatening disease, methotrexate alone may be enough to bring the disease under control without resorting to the more potent drugs.
Remission and the Risk of Relapse
The good news is that roughly 81% of patients with ANCA-associated vasculitis achieve complete remission within one year of diagnosis. The challenge is staying there. In a European cohort followed for a median of nearly five years, 31% of patients experienced a relapse or died within that period. Relapse was more common in granulomatosis with polyangiitis (41%) than in microscopic polyangiitis (26%), and it tended to occur about two to three years after diagnosis.
This relapse pattern is why ongoing monitoring and maintenance treatment are so important. Vasculitis is typically a chronic condition that requires long-term follow-up even when you feel well.
Who Manages Your Care
Vasculitis rarely stays in one lane. Because it can affect the kidneys, lungs, skin, nerves, and other organs simultaneously, care often involves a team. Rheumatologists typically lead treatment, since vasculitis falls under the umbrella of autoimmune and inflammatory disease. Nephrologists get involved when the kidneys are affected, which is common in small vessel vasculitis. Pulmonologists evaluate lung involvement, particularly in ANCA-associated types that frequently damage the lungs. Depending on your symptoms, dermatologists, neurologists, or ophthalmologists may also play a role.
Some academic medical centers have dedicated multidisciplinary vasculitis clinics where these specialists see patients together, which can streamline what would otherwise require multiple separate appointments. If you have a confirmed or suspected vasculitis diagnosis, getting care from a team with specific vasculitis experience can make a meaningful difference in how your disease is managed over time.