An Autopsy Case of Renal-Limited Granulomatosis With Polyangiitis Presenting With Acute Renal Failure and Initial Delirium.

Granulomatosis with polyangiitis (GPA) has three clinicopathological features, namely, necrotizing granulomatosis of the upper respiratory tract and lungs, focal segmental necrotizing glomerulonephritis of the kidney, and necrotizing vasculitis of small vessels throughout the body. A 92-year-old man with clinically diagnosed probable Alzheimer's disease (AD) exhibited subacute deterioration in cognitive function. On admission, he was diagnosed with acute renal failure with an elevated creatinine level (5.48 mg/dL) as well as severe disturbance of consciousness. Antineutrophil cytoplasmic antibodies (ANCAs) directed against proteinase 3 (PR3-ANCA) were highly positive with ≥ 350 U/mL. The patient was diagnosed with GPA and was managed with steroid pulse therapy. However, he died without any improvement in renal function. As a result of the autopsy, the patient was diagnosed with definite AD, and his impaired consciousness was found not to be caused by central nervous system involvement due to GPA. As necrotizing crescentic glomerulonephritis was observed, the cause of the acute progressive renal failure was found to be PR3-ANCA-positive GPA. The autopsy revealed no GPA-related lesions in other parts of the body aside from the kidneys. It is rare to encounter cases of PR3-ANCA-positive GPA with renal-limited vasculitis and acute renal failure as the initial manifestation, as in the present case. Making an accurate clinical diagnosis of older patients suffering from various diseases in multiple organs is challenging. Although autopsy has the limitation of a terminal image, it is extremely useful in elucidating the pathophysiology of the older patient in this case.