Aneurysmal rupture in microscopic polyangiitis: a case-based review

Microscopic polyangiitis (MPA) affects small and medium vessel, which sometimes leads to arterial aneurysms. In English database, only 15 reports refer to ruptured aneurysms in MPA. We experienced a fatal case with MPA who developed multiple visceral aneurysms, resulting in rupture of the hepatic aneurysm. For the better knowledge of aneurysmal rupture in MPA, we reviewed the feature of 16 cases, including our case. Organ involvement observed was glomerulonephritis 100%, pulmonary involvement 25%, peripheral neuropathy 25%, and purpura 12.5%. Locations of ruptured aneurysms were left gastric artery 31.25%, renal and hepatic artery 18.75% each, intracranial and splenic artery 12.5% each, and gastroepiploic and mesenteric artery 6.25% each. Median time to rupture was 45 days after systemic symptom onset, and 15 days after immunosuppressive treatment induction. Symptoms at rupture were visceral pain 68.75% and hemodynamic instability 62.5%. Pathological findings of ruptured aneurysms were acute vasculitis in 5, no evidence of active inflammation in 3. Causes of death were aneurysmal rupture in 5, treatment complications in 3, and total mortality rate was 50%. In conclusion, the initial presentation of MPA resulting in ruptured aneurysms tends to be renal-limited vasculitis. Aneurysms of abdominal medium-sized arteries tend to rupture, from 4 weeks after systemic symptom onset to 2 weeks after immunosuppressive treatment induction. Most aneurysms are less than 10 mm in diameter, develop asymptomatically in a few days, and are recognized when they rupture. Early induction of immunosuppressive treatment has the potential to shrink aneurysms and prevent rupture.