Microscopic Polyangiitis (MPA)
Microscopic polyangiitis (MPA) is a type of vasculitis that affects small blood vessels like capillaries, venules or arterioles. Vasculitis is a condition in which blood vessels are inflamed. They are autoimmune disorders, where the body produces antibodies against its own self. MPA usually affects adults in their 50s. Males suffer from this condition slightly more often than females. The reason why MPA affects some people is not known. It often targets the lungs and kidneys. Nerves, digestive tract and skin may also be involved.
The patient may show general signs and symptoms like fever, muscle pain and weight loss. He may suffer from complications like kidney failure, bleeding in the lungs or perforation in the digestive system. Blood tests, imaging studies like x-ray and CT scan and biopsy of the affected organ are used to diagnose the condition. The blood level of a specific antibody called ANCA is high in patients with MPA. The patient is treated with drugs that suppress immunity like cyclophosphamide and corticosteroids.
MPA shares some common features with another vasculitis i.e. Wegener’s granulomatosis. Patients with MPA develop kidney disease similar to Wegener’s granulomatosis. Blood levels of ANCA are high is both conditions. However, unlike in Wegener’s granulomatosis, accumulations of cells called granulomas are not seen in MPA. MPA affects the smallest blood vessels, while Wegener’s granulomatosis usually affects the medium sized blood vessels. Wegener’s granulomatosis often affects the upper airways. Upper airway disease is usually not seen in MPA.
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MPA should also be differentiated from another vasculitis called Polyarteritis Nodosa. In MPA, very small vessels like capillaries, venules or arterioles are inflamed. These vessels are usually not affected in Polyarteritis Nodosa.