Introduction:
Microscopic polyangiitis (MPA) is a condition that is the inflammation of blood vessels. This can affect kidneys, nerves, lungs, skin, and joints. Microscopic polyangiitis is a rare condition that can damage organ systems. Angiitis means inflammation of the blood vessels; therefore, microscopic polyangiitis occurs due to blood vessel inflammation. Although it is a rare disease, it can severely damage organ systems such as the liver, kidneys, nerves, joints, and skin. The condition is similar to granulomatosis polyangiitis, also known as Wegner’s granulomatosis, as both conditions are a form of vasculitis. Therefore the treatment is similar for both.
What Is Vasculitis?
It is the inflammation of blood vessels. The inflamed blood vessel becomes weak and stretches. This leads to an aneurysm. In some cases, the vessel ruptures, causing bleeding into the tissues. Vasculitis can also cause the blood vessel to become narrow and eventually closing off the vessel completely. This, in turn, leads to the lack of supply of oxygen and nutrients to the organs damaging them. This condition mainly affects small to medium-sized vessels.
What Are the Causes of Microscopic Polyangiitis?
MPA is not a form of cancer, but its exact cause is unknown. It does not spread and is not generally inherited. The immune system is believed to have a critical role in the condition. The immune system causes tissue and blood vessel inflammation.
What Are the Clinical Features of Microscopic Polyangiitis?
MPA is a rare condition and can affect men and women equally. Due to multiple organ involvement in the condition, the signs and symptoms also are many.
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Patients feel tired and fatigued.
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Fever.
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Loss of appetite.
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Weight loss.
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Depending on the site of involvement, rashes, joint pain, and muscle pain can also occur.
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When the lung is involved, cough, shortness of breath, and cough up of blood can occur.
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Nerve involvement causes numbness and loss of strength, which is preceded by abnormal sensations.
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Kidney involvement does not produce symptoms; hence the inflammation of the kidney is not apparent until the kidneys stop working. Therefore if vasculitis is suspected, urine should be examined.
How to Test Microscopic Polyangiitis?
Various steps are taken to diagnose microscopic polyangiitis, such as:
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Medical History: A detailed medical history is taken to detect the presence of MPA symptoms.
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Physical Examination: For the detection of organ involvement.
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Blood Tests: The site of organ involvement is identified, and antineutrophil cytoplasmic antibodies (ANCA) are also performed.
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Urine Analysis: Urine is analyzed to detect the presence of red blood cells or proteins.
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Imaging Tests: Computed tomography (CT), magnetic resonance imaging (MRI), and X-rays are taken to determine abnormalities in organs such as the lungs.
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If ANCA is tested positive, MPA can be suspected but not proven.
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If suspected, a biopsy is done of the tissue sample to confirm the presence of vasculitis. The biopsy is done of the tissue in doubt, where the abnormal findings have been detected by other examinations, imaging tests, or laboratory tests.
How to Treat Microscopic Polyangiitis?
Since the immune response is believed to cause MPA, the primary treatment includes medications that suppress the immune system. Immunosuppressive medications can have side effects.
Corticosteroids:
Patients suffering from MPA who have critical organ failure are treated with corticosteroids. In some cases, corticosteroids are mixed with other immunosuppressive agents such as Rituximab and Cyclophosphamide. In less severe cases, corticosteroids are combined with Methotrexate. The treatment with corticosteroids is to prevent injuries arising from MPA. Once the condition improves, the steroid is tapered and eventually stopped. Cyclophosphamide is only used till remission is observed. Once improvement is observed, Cyclophosphamide is replaced with another immunosuppressive agent such as Methotrexate, Mycophenolate mofetil, and Azathioprine to sustain the improvement. These medications are generally used for treating other conditions, such as:
- Azathioprine and Mycophenolate are used to prevent organ transplant rejection.
- Methotrexate is given for psoriasis and rheumatoid arthritis.
- Methotrexate and Cyclophosphamide are used to treat cancer. The doses at which these medications are used to treat cancer are much less than when used for cancer (10 to 100 times lower). The principle is to use it to provide immunosuppression.
- Rituximab targets the immune system and is as effective as Cyclophosphamide.
Treatment Time:
The time taken for the treatment, and the longevity of the remission medications changes from person to person. In most cases, it takes one to two years before tapering the dose and eventual discontinuation.
Risk Of Immunosuppressive Agents:
Patients on immunosuppressive agents have the complication of developing serious infections. In addition, the potential side effect varies with the drug used. Therefore, this must be kept in mind and regularly monitored to minimize complications. In some cases, the medications may be well tolerated at the beginning of the treatment, but the tolerance can vary over a period of time. Therefore there is a need for long-term monitoring of the drug, even after it is stopped.
What Is the Prognosis of Microscopic Polyangiitis?
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The condition is rare; the prognosis is not well-defined.
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80 percent of the affected population has survived after five years of illness.
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The survival rate is proportional to the severity of the illness.
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If recognized and treated early, organ failure can be minimized. In addition, remission can be promptly attained in cases that are closely monitored.
Relapse: There is a 50 percent chance of relapse. The symptoms may or may not be similar to the ones experienced the first time. Chances for the severity of the relapse can be reduced if the patient consults the doctor as early as the symptoms appear. The treatment follows the same pattern as that of the newly diagnosed disease. Even relapse cases can achieve remission.
Conclusion:
Microscopic polyangiitis is a rare condition that arises due to vasculitis or the inflammation of blood vessels. The inflammation causes the blood vessels to expand and stretch or causes them to narrow and eventually completely close off. This leads to reduced oxygen and blood supply to the organs leading to organ failure. It is believed to occur due to the immune response of the body, and therefore the treatment option comprises using immunosuppressive medications.
