ANCA-Associated Vasculitis

Overview

ANCA-associated vasculitis (AAV) is a group of uncommon autoimmune conditions in which the immune system inflames the body’s smallest blood vessels. Because these vessels supply every organ, the disease can affect many parts of the body at once — most importantly the kidneys, lungs, sinuses and nerves. The name comes from an antibody found in the blood of most people affected, the anti-neutrophil cytoplasmic antibody, or ANCA.

There are three main types. Granulomatosis with polyangiitis (GPA) tends to involve the sinuses, nose, ears and lungs as well as the kidneys. Microscopic polyangiitis (MPA) most often affects the kidneys and lungs. Eosinophilic granulomatosis with polyangiitis (EGPA) occurs in people with adult-onset asthma and a high level of a white cell called the eosinophil. They are grouped together because they share the ANCA antibody and respond to similar treatment.

AAV can range from disease limited to the sinuses or skin through to a rapidly progressive illness that threatens the kidneys or lungs within days. This is why it is treated as a condition that needs prompt specialist assessment, and why close monitoring continues long after the first flare has settled.

Symptoms

Many people first feel generally unwell for weeks or months — with fever, tiredness, weight loss, and aching joints and muscles — before the specific features appear. Because these early symptoms are vague, the diagnosis is often not obvious at the start.

The specific symptoms depend on which organs are involved. In GPA there may be persistent blocked or crusty nose, nosebleeds, sinus pain, or ear problems and hearing loss. Lung involvement can cause cough, breathlessness, or coughing up blood. The kidneys may be affected silently, showing only as blood or protein in the urine, which is why urine testing is so important. Inflamed nerves can cause numbness or weakness, often in a hand or foot, and the skin may show a rash of small purple spots. In EGPA, worsening asthma and nasal polyps are typical.

Causes and risk factors

The trigger for AAV is usually unknown. It develops when the immune system mistakenly activates and damages the lining of small blood vessels, and both an inherited susceptibility and environmental factors are thought to contribute. A small number of cases are linked to particular medicines or, rarely, infections.

AAV is not contagious and is not inherited in a simple, direct way. It can occur at any age but is most common in adults from middle age onwards, and GPA and MPA affect men and women roughly equally. It is not caused by anything a person did or could have prevented.

Diagnosis

The diagnosis is made by bringing together the pattern of symptoms, blood and urine tests, imaging, and — wherever possible — a biopsy of an affected organ such as the kidney, skin, or nose. A biopsy that shows the typical inflammation gives the firmest diagnosis and helps guide treatment.

Blood tests for ANCA are central. Two patterns are measured, directed against proteins called PR3 and MPO; PR3-ANCA is more often seen in GPA and MPO-ANCA in MPA, though there is overlap. A positive ANCA strongly supports the diagnosis in the right clinical setting, but the whole picture matters, because the antibody can occasionally be found in other conditions. Because the kidneys can be involved without symptoms, urine is always checked, and any sign of kidney inflammation is treated as urgent.

Investigations

Initial tests usually include ANCA (with PR3 and MPO patterns), inflammation markers (ESR and CRP), a full blood count, and kidney function. Urine is examined for blood and protein, and if kidney inflammation is suspected a kidney biopsy is arranged. A chest X-ray or CT scan looks for lung involvement, and in EGPA the eosinophil count is followed.

These tests are also used over time to judge how active the disease is and to catch a relapse early. Monitoring continues during quiet periods, because AAV can flare again months or years later, and an early flare is far easier to control than an advanced one.

Treatment

Treatment has two stages. The first, remission induction, brings active disease under control quickly, usually with steroids combined with either rituximab or cyclophosphamide. Current guidance favours rituximab for many people and places clear emphasis on reducing the steroid dose rapidly once the disease is responding, because much of the harm in AAV over time comes from prolonged high-dose steroids. Severe kidney or lung disease may need additional treatments such as plasma exchange in selected cases.

Once the disease is quiet, the second stage — maintenance — keeps it in remission, typically with lower-intensity treatment such as repeated rituximab for a defined period. Because these medicines lower the immune system, care includes preventing infection: certain vaccinations, a medicine to prevent a specific chest infection, and prompt attention to any new infection are all standard. The exact plan is tailored to the type of AAV, which organs are affected, and how the disease has behaved.

Living with ANCA-associated vasculitis

With modern treatment, most people with AAV reach remission and lead full lives, but it is a long-term condition that needs ongoing partnership with the rheumatology team. Attending regular blood and urine checks is the single most useful thing a person can do, because it is how a relapse or a treatment side effect is caught early.

Preventing infection matters: keeping recommended vaccinations up to date, not ignoring fevers, and knowing which symptoms need urgent review all help. Not smoking, and looking after blood pressure, kidney health, and bone strength — which steroids can weaken — are part of long-term care. Knowing the early signs of a flare, such as returning nasal or urinary symptoms, means treatment can be adjusted before the disease advances.