純粋自律神経不全症の病理

Pathological Study of Pure Autonomic Failure

純粋自律神経不全症は，レビー小体病の一型で，末梢自律神経系を病変の首座とする。診断には，多系統萎縮症，アミロイドーシスを中心とする末梢神経障害の除外が必要で，前者にはMRI，後者には神経伝導速度検査，腓腹神経生検が有用である。MIBG心筋シンチグラフィ陽性，発汗障害をもとに行った皮膚生検でレビー小体病理を高率に認めた。長期経過においては認知症状が加わることが多く，小阪憲司博士が提唱したびまん性レビー小体病の病理像に合致する。末梢性の要素に加え，中枢性要素との複合が特徴的であり，進行が緩徐であるため両者への配慮が必要である点において，脳神経内科の関与が重要な疾患領域である。

Abstract

Pure autonomic failure (PAF) is a subtype of Lewy body disease whose main target is the peripheral autonomic nervous system. The differential diagnosis includes multiple system atrophy and small fiber neuropathy like amyloidosis. Low uptake of ¹²³I- metaiodebenzyl guanidine (MIBG) cardiac scintigraphy is of diagnosis use. Biopsy of skins affected with decreased sweating could prove Lewy pathology in the peripheral autonomic nerves. Among more than 10,000 autopsy cases in BBAR (Brain Bank for Aging Research), representing an aging cohort in Tokyo metropolitan suburban area, only two cases had clinical diagnosis of PAF. Orthostatic hypotension without parkinsonism is common clinical features. Both presented with diffuse Lewy body pathology involving the peripheral autonomic nervous system, brain stem, limbic system and neocortex with mild loss of pigmented neurons in substantia nigra. Other senile changes like Alzheimer pathology, argyrophlic grains and TDP43 (TAR DNA- binding protein of 43kDa) proteinopathy were mild. Neuropathological features fulfilled morphological criteria of dementia with Lewy bodies (DLB) pure neocortical form, suggesting dementia as one of the late clinical complications. About one third of autopsy cases registered to BBAR contained Lewy pathology in the body, among whom, 5% had Lewy pathology only in the peripheral autonomic nervous system. These cases may be the earliest stage of PAF.