Vasculitis is a group of diseases in which the immune system attacks blood vessel walls, causing inflammation that can narrow, weaken, or block the vessels. This disrupts blood flow to organs and tissues, potentially causing damage anywhere in the body. There are more than 20 types, classified mainly by the size of blood vessels affected: large, medium, or small.
How Vasculitis Damages Blood Vessels
In a healthy immune system, white blood cells and antibodies target foreign invaders like bacteria or viruses. In vasculitis, this defense system misfires and turns against the walls of blood vessels instead. The specific way this happens varies by type, but three main mechanisms drive the damage.
In some forms, certain immune cells migrate into the vessel wall and recruit other inflammatory cells, triggering a chain reaction. These cells release chemical signals that cause the vessel lining to thicken over time, gradually choking off blood flow. Giant cell arteritis, which targets large arteries, works this way.
In other types, clumps of antibodies called immune complexes deposit along vessel walls. These deposits activate nearby white blood cells, which release enzymes that erode the vessel from within. This can cause the vessel to leak, form small bulges (micro-aneurysms), or become completely blocked. Organs downstream lose their blood supply, and tissue death can follow.
A third mechanism involves antibodies that mistakenly target enzymes inside white blood cells themselves. When these antibodies latch onto white blood cells near a vessel wall, they essentially activate those cells in the wrong place at the wrong time, punching holes in small blood vessels. This is the driving force behind a group called ANCA-associated vasculitis, which primarily damages the kidneys and lungs.
Types Based on Vessel Size
Vasculitis is organized by the size of vessels it most commonly affects, though overlap exists.
Large vessel vasculitis targets the aorta (the body’s main artery) and its major branches. Giant cell arteritis is the most common form, occurring almost exclusively in people over 50 and more often in women. It causes headaches, scalp tenderness, jaw pain, and can lead to sudden vision loss if the arteries supplying the eyes are involved. Takayasu arteritis, the other major type, tends to affect younger adults and can cause arm or leg pain during activity due to blocked arteries.
Medium vessel vasculitis strikes the arteries that supply specific organs, like the kidneys, intestines, or heart. Polyarteritis nodosa is the best-known example. It can cause micro-aneurysms, kidney damage, and abdominal pain.
Small vessel vasculitis affects the tiniest blood vessels: capillaries, small veins, and small arteries. This is where ANCA-associated vasculitis falls, including three subtypes. Granulomatosis with polyangiitis (GPA) often starts with chronic sinus problems, nasal crusting, and lung nodules before progressing to kidney disease. Microscopic polyangiitis (MPA) typically hits the kidneys and lungs. Eosinophilic granulomatosis with polyangiitis (EGPA) is closely linked to adult-onset asthma and high levels of a specific white blood cell type. All three are rare. The global incidence for ANCA-associated vasculitis combined is about 17 cases per million people per year, with GPA being the most common at 9 per million.
Symptoms to Recognize
Because vasculitis can affect virtually any organ, symptoms vary widely depending on the type. Most forms share a set of general, whole-body symptoms: fever, unexplained weight loss, fatigue, and widespread aches and pains. These can easily be mistaken for an infection or general illness, which is one reason vasculitis often takes time to diagnose.
Organ-specific symptoms develop as inflammation targets particular blood vessels:
- Skin: Red or purple spots (purpura), especially on the legs, caused by leaking small vessels. Ulcers or lumps under the skin can also appear.
- Eyes: Redness, itching, burning, double vision, or partial vision loss. Giant cell arteritis can cause brief episodes of blindness that become permanent without treatment.
- Kidneys: Blood or protein in the urine, often with no pain. Left unchecked, this can progress to kidney failure.
- Lungs: Coughing, shortness of breath, or coughing up blood.
- Nerves: Numbness, tingling, or weakness in the hands or feet.
- Digestive system: Pain after eating, ulcers, or blood in the stool from inflamed intestinal blood vessels.
What Causes It
Most vasculitis arises without a clear external trigger. The immune system begins attacking blood vessels for reasons that remain poorly understood, likely involving a combination of genetic susceptibility and environmental factors. This is called primary vasculitis.
Secondary vasculitis, on the other hand, is set off by something identifiable. Infections are one well-known trigger: hepatitis B and hepatitis C can both provoke vessel inflammation. Hepatitis C, in particular, is linked to a form called cryoglobulinemic vasculitis.
Certain medications can also trigger vasculitis. Hydralazine (a blood pressure drug), propylthiouracil (used for overactive thyroid), and cocaine are the most common drugs linked to ANCA-associated vasculitis specifically. NSAIDs, some antibiotics, and certain cancer therapies have been connected to other forms. Drug-induced vasculitis often improves once the offending medication is stopped, though some cases require additional treatment.
Vasculitis can also develop alongside autoimmune diseases like rheumatoid arthritis or lupus, where chronic immune activation spills over into blood vessel damage.
How Vasculitis Is Diagnosed
There is no single test that confirms vasculitis. Diagnosis typically involves piecing together blood work, imaging, and sometimes a tissue biopsy.
Blood tests look for signs of inflammation and immune activity. Markers of general inflammation are often elevated in untreated vasculitis and are useful for ruling the condition out, particularly for giant cell arteritis. ANCA testing is more specific: antibodies targeting two particular enzymes inside white blood cells are highly specific to GPA, MPA, and EGPA. A positive ANCA result in the right clinical context strongly supports a diagnosis.
Imaging studies, including CT scans, MRI, or specialized blood vessel scans, can reveal narrowing, bulging, or thickening of vessel walls. For large vessel vasculitis, imaging of the aorta and its branches is particularly important.
Biopsy remains the gold standard for many types. A small sample of affected tissue, often from the kidney, skin, lung, or a temporal artery, is examined under a microscope for patterns of inflammation. Different types of vasculitis leave distinct signatures: immune complex deposits along vessel walls, clusters of inflammatory cells called granulomas, or damage with very few immune deposits (called pauci-immune, typical of ANCA-associated disease).
In 2022, updated classification criteria from the American College of Rheumatology and EULAR introduced weighted scoring systems for ANCA-associated vasculitis subtypes. These combine clinical features, lab results, imaging, and biopsy findings into a point-based system, helping clinicians distinguish between GPA, MPA, and EGPA more reliably.
Treatment and What to Expect
The core strategy for vasculitis is suppressing the immune system enough to stop it from attacking blood vessels, while minimizing the side effects that come with dampened immunity. Treatment unfolds in two phases: bringing the disease under control (induction) and then keeping it quiet long term (maintenance).
Steroids are almost always part of the initial approach. They work quickly to reduce inflammation and are often started at moderate to high doses, then gradually tapered over weeks to months. The goal is to reach the lowest effective dose as soon as possible, since prolonged steroid use carries its own risks, including bone thinning, weight gain, and increased infection susceptibility.
For more serious or widespread disease, stronger immune-suppressing medications are added alongside steroids. Which one depends on the type and severity of vasculitis. For ANCA-associated vasculitis with severe flares, a biologic medication that depletes a specific type of immune cell (B cells) has become a standard part of care. Other options suppress the immune system through different pathways, and doctors may try several approaches to find the best balance of effectiveness and tolerability.
Treatment is not always well tolerated, and some cases prove resistant to standard therapies. Newer biologic medications targeting specific inflammatory signals have expanded the options, particularly for forms that don’t respond to conventional treatment.
Remission, Relapse, and Long-Term Outlook
Many people with vasculitis achieve remission, meaning the disease becomes inactive. In a large study of 427 patients with ANCA-associated vasculitis, 65% were able to stop all immune-suppressing medication at some point during follow-up. About half of those who stopped treatment stayed off it for two or more consecutive years, and nearly a quarter remained medication-free for five years or longer.
Relapse, however, is a real and ongoing concern. Even among patients who maintained remission off treatment for five or more years, some relapsed as late as 6 to 16 years after stopping medication. GPA tends to relapse more frequently than MPA. This means that even during periods of apparent remission, regular monitoring with blood tests and clinical evaluations remains important.
The long-term risks of vasculitis come from two directions. The disease itself can cause lasting organ damage, particularly to the kidneys, lungs, and eyes, especially if diagnosis or treatment is delayed. At the same time, the medications used to control vasculitis carry their own burden. Prolonged immune suppression increases the risk of serious infections and, over many years, certain cancers. Balancing these competing risks is the central challenge of managing vasculitis over a lifetime, and it requires close, ongoing partnership between patient and specialist.