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Therapeutics in Dermatology
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Polyarteritis nodosa and microscopic polyangiitis

24 June 2015, by PUECHAL X. & SIBILIA J.

Summary

POLYARTERITIS NODOSA

WHAT IS POLYARTERITIS NODOSA?

Polyarteritis nodosa is a very rare disease that is part of a group of diseases known as systemic vasculitis and it affects medium-sized blood vessels, especially those in the skin, heart, kidneys and the brain.

WHAT CAUSES POLYARTERITIS NODOSA?

Some cases of polyarteritis nodosa are linked to an acute hepatitis B virus infection (fewer than 10% of cases today) or very rarely to other viral infections (for example cytomegalovirus). Although it is certainly possible to pass on these viral infections, polyarteritis nodosa itself is not a contagious disease. A few cases of polyarteritis nodosa linked with a rare blood disease, hairy-cell leukaemia, have been described. However, the majority of the time the cause of the disease is unknown.

WHO IS AFFECTED BY POLYARTERITIS NODOSA?

Polyarteritis nodosa mainly affects adults between the ages of 30 and 50, with slightly more men than women affected according to some studies.

WHAT ARE THE SYMPTOMS OF THE DISEASE?

The symptoms of polyarteritis nodosa vary from one patient to another and include fever, fatigue, weight loss, loss of appetite, joint and muscle pain, skin outbreaks, swollen legs, skin ulcers and/or nodules.

The disease can manifest in other ways, such as abdominal pain or gastrointestinal bleeding. If the peripheral nerves are affected, patients may notice muscle weakness, tingling sensations or burning- or electric shock-type pains in the hands and/or feet. When the blood vessels of the brain are affected this can lead to a stroke, causing hemiplegia or seizures. When the arteries in the kidneys are affected this can cause severe high blood pressure and/or kidney failure. If the arteries in the heart (the coronary arteries) are affected, a heart attack, heart failure with lung oedema, or pericarditis (inflammation of the sac around the heart) can arise.

HOW IS THE DIAGNOSIS MADE?

There is no specific test to diagnose polyarteritis nodosa. A doctor can only make a diagnosis when a number of suggestive clinical signs occur together with positive results from a number of blood tests, radiology investigations, and the biopsy of an affected organ or tissue. Most patients show inflammation on laboratory studies (increased levels of CRP or raised erythrocyte sedimentation rate). An angiogram of the arteries (or arteriogram) of the digestive system or kidneys will often show the consequences of this inflammation of the vessels, with images showing narrowed areas (stenosis) alternating with areas of dilation (microaneurysms) and sometimes complete thromboses.

WHAT IS THE PROGNOSIS OF THE DISEASE?

A great deal of progress has been made over the last 30 years in the overall management (diagnosis and treatment) of polyarteritis nodosa. Without treatment, the disease is usually fatal within a few weeks or months. Today, in the vast majority of cases and when diagnosis is made early, the disease can quickly be brought under control and a cure achieved. Relapse is rare, but possible. Long-term monitoring is therefore required, even when the disease has disappeared.

WHAT IS THE TREATMENT FOR POLYARTERITIS NODOSA?

The treatment for forms related to the hepatitis B virus is a combination of corticosteroids over several days or weeks to control the inflammation, plasmapharesis to remove antibody-virus complexes from the blood that have been deposited into the vessel walls causing the inflammation, and antiviral medications, such as interferon alpha and lamivudine, to rid the body of the virus.

Patients who have polyarteritis nodosa that is not related to a viral infection will be treated with a combination of high-dose corticosteroids over several months, together with immunosuppressant drugs in the most serious cases.

MICROSCOPIC POLYANGIITIS

WHAT IS MICROSCOPIC POLYANGIITIS?

Microscopic polyangiitis (MPA) is characterised by inflammation of the small blood vessels, especially those in the kidneys, lungs, nerves and skin. More than 80-90% of patients have affected kidneys, which is the same as the figure for Wegener’s granulomatosis (extracapillary glomerulonephritis). However, the inflammatory lesions in microscopic polyangiitis do not entail granuloma formation.

This condition can sometimes affect medium-sized blood vessels, but this is not the predominant form. In these cases, it can be difficult to distinguish MPA from polyarteritis nodosa (PAN, the two should not be confused), which is another type of vasculitis that affects medium-sized blood vessels. It was only in 1994 that MPA was clearly defined as an individual disease in the Systemic Vasculitis Nomenclature that was set out at the Chapel Hill Consensus Conference. Prior to this, PAN and MPA had very often been confused with one another although there are significant clinical differences between them.

WHAT CAUSES MICROSCOPIC POLYANGIITIS?

We do not know exactly what causes this type of vasculitis, and in fact there is unlikely to be one single cause. We do, however, know that it is not contagious.

WHO IS AFFECTED BY MICROSCOPIC POLYANGIITIS?

MPA can develop at any age. However, it mainly appears in adults between the ages of 40 and 60, affecting males and females in equal numbers. It almost exclusively affects white people (sometimes called ‘Caucasians’). It seems to be more common than Wegener’s granulomatosis in Asia.

WHAT ARE THE SYMPTOMS OF THIS DISEASE?

MPA is a systemic disease, which means that it can affect any of the organs or tissues in the body. The most common signs early on in the disease are fever, muscle and joint pain, fatigue and general weakness, as well as weight loss that is unrelated to a diet. Involvement of the kidneys, which is very common, is generally “silent” at first, and it is only detected on urine tests (traces of blood and/or albumin are detected on a urine dipstick test and urine studies under a microscope). Sometimes, when kidney involvement is more severe or advanced, the amount of urine passed in a day decreases and the urine becomes dark in colour. When the lungs are affected it is in the form of an inflammation of the capillaries in the lungs, which means that they become abnormally permeable to blood, resulting in bleeding into the alveolar spaces. There is rarely a significant amount of bleeding, but it can cause shortness of breath, chest pain, and sometimes coughing up blood and anaemia. Doctors may speak of a pulmonary-renal syndrome when both the kidneys and lungs are affected.

Other organs can be affected, such as the peripheral nerves (neuropathy that translates into a tingling feeling in the feet and/or hands, or a loss of muscle strength when performing certain movements), the skin (purpura, ulceration on the skin of the legs), or digestive tract (abdominal pain or blood in the stools that is red or black if it comes from the stomach).

HOW THE DIAGNOSIS IS MADE?

Over 80% of patients with MPA have certain antibodies known as ANCA in their blood, and these are usually targeted against a protein called myeloperoxidase (these may be referred to as anti-MPO ANCA).

Other blood and urine tests, x-rays, CT scans, and especially tissue or organ biopsies, in particular kidney biopsies, are usually needed to make a diagnosis and decide on the most suitable treatment.

WHAT IS THE PROGNOSIS OF THIS DISEASE?

In the same way as with Wegener’s granulomatosis, in which patients often also have ANCA antibodies (usually targeted against a different protein, called PR3), there is no treatment that is 100% effective, but with early and appropriate management in a specialised centre, the very large majority of patients will achieve disease remission. We use the word remission, rather than cure, because relapses are quite common, affecting around 30% of patients. However, a diagnosis of relapse is generally made more quickly, since the patient is already known to have MPA, which means that treatment can be started sooner and at a less advanced stage of the disease.

WHAT IS THE TREATMENT FOR THE VASCULITIS MICROSCOPIC POLYANGIITIS?

Corticosteroids and immunosuppressant drugs are usually prescribed when a patient’s kidneys and/or lungs are affected in order to achieve disease remission and then to reduce the risk of relapse. Sometimes, in the most serious cases, plasmapharesis may be added to these treatments. High doses of the treatment will be prescribed at first (to induce remission) then, after six months of treatment on average, the doses of medications are reduced and the immunosuppressant drugs changed for less aggressive agents in order to maintain long-lasting remission. The whole course of treatment will last a minimum of 18 months. Other treatments do exist (such as rituximab) but they are at present only used in serious forms or those that do not respond to the standard treatments.

In some moderate forms of the disease, in particular when it is only the skin that is affected, it is possible that initially treatment may consist of steroids only, with immunosuppressants kept in reserve for steroid-resistant cases.

WHAT IS VASCULITIS?

Vasculitis is a disease that is defined by the existence of inflammation of the blood vessels, arteries, veins and/or capillaries. The term vasculitis covers several different diseases, some of which can be life-threatening. For the most part their causes are unknown, but with advances in medicine that have been made over the last 20 years, treatments are available today that make it possible to improve the course of these diseases very significantly.

Continued biomedical research and research into treatments remains essential in the field of vasculitis so that management of these diseases can be improved and eventually a cure may be found.

ABOUT THE VASCULITIS FOUNDATION 

The Vasculitis Foundation (VF, previously Wegener’s Granulomatosis Association) is the largest international association providing support and information for patients with vasculitis and their families and carers.

The objectives of VF, delivered via its website, periodical publications, information leaflets, close relationships with numerous researchers and specialist doctors, meetings, and the creation and support of many patient groups throughout the world, are to improve understanding, help to promote research, and to be able to provide all the necessary information about vasculitis to patients and their families and friends, in order to be better able to combat the disease.

About the association Wegener Infos Vascularites (Wegener and Vasculitis information) and the Groupe Français d’Etude des Vascularites (French Vasculitis Study Group, http://www.vascularites.org).

The Groupe Français d’Etude des Vascularites is a treatment and biomedical research group created in the early 1980s in France. This group provides scientific advice to the French patient association for vasculitis, Wegener Infos et Vascularites, which was created in January 2006 and is the equivalent of VF in France.

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