Fatal hemoperitoneum due to rupture of mesenteric artery in remission state of microscopic polyangiitis, concomitant with severe hypertension and posterior reversible encephalopathy syndrome: an autopsy case report.

Microscopic polyangiitis (MPA) is a type of necrotizing vasculitis associated with high levels of myeloperoxidase-specific antineutrophil cytoplasmic antibody (MPO-ANCA). While generally associated with renal dysfunction, MPA can also cause intraabdominal hemorrhage in rare cases. A 66-year-old man was admitted to our hospital for renal dysfunction, numbness, and weight loss for 3 months. He had no significant medical history. Renal biopsy revealed crescentic glomerulonephritis with necrotizing vasculitis, which was associated with a high serum titer of MPO-ANCA, leading to a diagnosis of MPA. Remission-induction treatment with glucocorticoids and rituximab was initiated, which improved the patient's general condition and renal failure. His blood pressure was elevated and was controlled by amlodipine treatment. Two months after discharge, he visited the emergency department because of chest pain. A diagnosis of acute cardiovascular syndrome was suggested; however, his cardiac artery was not stenotic. The patient's blood pressure was high despite antihypertensive therapy, and he developed posterior reversible encephalopathy syndrome (PRES). Despite intensive treatment, the patient died 3 days later. An autopsy revealed that the cause of death was hypovolemic shock due to massive intra-abdominal hemorrhage from the ruptured mesenteric artery involved in vasculitis. In cases of MPA with sudden-onset chest or abdominal pain, a ruptured intra-abdominal artery should be considered. Secondary hypertension associated with vasculitis should be carefully managed to prevent hemorrhagic complications and PRES.