脳アミロイドアンギオパチー関連炎症・血管炎

Cerebral Amyloid Angiopathy-Related Inflammation/Vasculitis

脳アミロイドアンギオパチー関連炎症・血管炎は，脳の皮質・髄膜血管に沈着したアミロイドβ蛋白に対する免疫反応によって炎症が生じたもので，わが国の推定患者数は170人である。急性または亜急性に認知機能障害などを呈し，頭部MRIで出血を伴う白質脳症が見られる。病理では血管周囲へのリンパ球浸潤や多核巨細胞を伴う肉芽腫性血管炎を認める。免疫療法で改善が見込めるため，すみやかな診断および治療開始が推奨される。

Abstract

Cerebral amyloid angiopathy (CAA) is a disorder characterized by the deposition of amyloid in the leptomeningeal and cortical blood vessels. Sporadic amyloid β (Aβ)-type CAA is the most common form of CAA. Although CAA is a well-known cause for recurrent cerebral lobar hemorrhage, inflammation, and vasculitis, CAA-related inflammation/vasculitis (CAA-ri/vasculitis) induced by Aβ deposition on vessel walls is emerging as a treatable condition. The estimated total number of cases of and prevalence of CAA-ri/vasculitis in Japan were 170 and 0.13 per 100 000 population, respectively. Patients with CAA-ri/vasculitis show acute or subacute-onset of cognitive impairment, behavioral changes, and headache. Brain magnetic resonance imaging, showing asymmetrical white matter abnormalities and occasional meningeal enhancement, is a useful tool for the diagnosis of CAA-ri/vasculitis. Moreover, elevation of anti-Aβ antibodies and inflammatory markers in the cerebrospinal fluid can help in clinical diagnosis. Although several clinical diagnostic criteria have been proposed, neuropathological examination of a brain biopsy remains the gold standard for detecting severe Aβ deposition and vasculopathic changes with lymphocytic infiltrations and/or granulomatous vasculitis. No validated treatment regimen has been established to date. Nearly 80% patients with CAA-ri/vasculitis improved after immunosuppressant therapy with corticosteroid and/or cyclophosphamide. Early treatment is essential to prevent irreversible sequelae in the brain.