内服治療で十分な効果が得られない小径線維ニューロパチー—小径線維ニューロパチーの原因診断と治療選択

Small Fiber Neuropathy with Inadequate Response to Medical Therapy: Diagnosis of The Etiology of Small Fiber Neuropathy and Treatment Option

小径線維ニューロパチー（SFN）は有意な検査所見に乏しく診断に難渋する。当科で経験した症例では，各種検査で異常を検出できず，対症的治療への反応も乏しかったが，電流知覚閾値検査で異常を認め，血中抗Plexin D1抗体陽性を認めたことから自己免疫性SFNと診断し，血漿交換療法が著効した。SFNの一般的治療や新型コロナウイルス感染症関連についても紹介する。

Abstract

Small-fiber neuropathy (SFN) has few significant laboratory findings and is difficult to diagnose. In 70% of the cases, the cause of SFN is unknown. Among the cases with known etiology, 50% are associated with diabetes, and the causes are autoimmune, amyloidosis, or multifactorial. In recent years, a specific autoantibody-positive group has been identified and has attracted attention because immunotherapy was successful in the autoantibody-positive SFN groups. In the cases reporting to our department, abnormalities could not be detected by various tests, including nerve conduction studies, and the response to symptomatic treatment was poor. An abnormality was identified in the current perception threshold test result, and a positive blood anti-plexin D1 antibody was detected via enzyme-linked immunosorbent assay. Therefore, autoimmune SFN was diagnosed, and plasma exchange therapy was remarkably effective. Subsequently, we aim to introduce general treatments for SFN and COVID-19-related SFN.