Microscopic Polyangiitis: Symptoms, Causes, Treatment

It belongs to the ANCA-associated vasculitis group, although antibody tests can be negative. It differs from related disorders with prominent allergic or granulomatous features.

Related reading: Assessment of new symptoms in autoimmune disease.

Fatigue, fever, weight loss, rash or limb numbness and weakness may occur. Kidney damage may initially be silent; lung involvement can cause breathlessness or coughing blood.

Immune activity inflames small blood vessels, often without an identifiable cause. It is not contagious, and a single symptom or laboratory result cannot establish its origin.

The condition often develops in middle or later adulthood but is not restricted to those ages. Associated antibodies alone do not establish disease; clinical correlation is essential.

Assessment includes urine, kidney-function and blood tests, antibody testing and organ-directed imaging. Biopsy may be needed; an antibody result alone does not confirm the diagnosis.

Organ-threatening disease may require rituximab or cyclophosphamide with corticosteroids under specialist care, followed by maintenance treatment. Plasma exchange is not routine for every patient.

Permanent kidney damage, kidney failure, pulmonary bleeding and nerve injury can occur. Relapse is possible after improvement; immune-suppressing treatments also increase infection risk and require monitoring.

There is no established way to prevent onset. Follow-up, urine and kidney monitoring, treatment adherence and infection-prevention planning help detect relapse and reduce complications.