Aneurysms of the renal arteries associated with segmental arterial mediolysis in a case of polyarteritis nodosa

This is the first report of segmental arterial mediolysis (SAM) accompanied with polyarteritis nodosa (PN), and manifesting aneurysms of the renal arteries. A 73‐year‐old woman was admitted to hospital because of a high fever. Laboratory tests showed leukocytosis with increased CRP level in the serum. Myeloperoxidase‐anti‐neutrophil cytoplasmic antibody (MPO‐ANCA) and proteinase 3 (PR3)‐ANCA were negative. There were no signs indicating infection or malignancy. After admission renal function rapidly deteriorated. Treatment was then started with daily oral prednisolone and hemodialysis. On the 40th day of hospitalization the patient suddenly became comatose. Cranial CT showed a subarachnoid hemorrhage. The patient died and an autopsy was performed. The pathological findings showed necrotizing vasculitis of the small arteries in various organs, but not associated with that of arterioles or renal glomerular lesions, indicating PN. Unexpectedly, the segmental arteries of the bilateral kidneys showed vascular lesions of dissecting aneurysms, indicating SAM. This case indicates that SAM is one of the causes of aneurysms in PN and is clinically important when the clinical course of PN patients rapidly advances.