不整脈原性右室心筋症と初期診断された心臓サルコイドーシスの1例

A Case of Cardiac Sarcoidosis Mimicking Arrhythmogenic Right Ventricular Cardiomyopathy

要旨　症例は，30歳男性．動悸を自覚し，心電図検査にて右脚ブロックとV_1～4での陰性T波，非持続性心室頻拍を指摘された．心エコー図では，左室は正常だが，右室が著明に拡大していた．電気生理学的検査で心室細動が誘発され，診断基準に基づき不整脈原性右室心筋症(ARVC)と判断された．しかし，両側肺門部リンパ節の腫脹を認め，結節性皮疹から皮膚サルコイドーシスと組織診断された．心臓MRIでの右室炎症像を含めても，診断基準を満たさなかったが，心臓サルコイドーシス(CS)が強く疑われたため，植込型除細動器を留置した後に，ステロイド治療を開始した．

　ARVC診断基準は，特異度が必ずしも十分でない．一方，CS診断手引きは左室病変を念頭に置き，右心優位のCSでは確定診断に至らぬ可能性がある．したがって，診断基準上ARVCと確定されても，他疾患の可能性を安易に排除せず，CSを含めた除外診断を進めるべきである．

　A 30-year-old man with palpitations due to nonsustained ventricular tachycardia was referred to our hospital. His electrocardiogram revealed negative T waves in leads V1-V4 and a right bundle branch block, while his echocardiogram indicated normal left ventricular function but a markedly dilated right ventricle with impaired contraction. Provisional arrhythmogenic right ventricular cardiomyopathy(ARVC)was diagnosed on the basis of the criteria of the Task Force of the European Society of Cardiology and the International Society and Federation of Cardiology(ESC/ISFC). In addition to bilateral hilar lymph node swellings, sarcoidosis revealed through histological examination of skin eruptions, and abnormal cardiac magnetic resonance images(atypically predominant in the right ventricle)led to the suspected diagnosis of cardiac sarcoidosis(CS). After inserting an implantable cardioverter defibrillator, we employed steroid therapy for CS. After therapy, the patient's palpitations disappeared and his ventricular arrhythmia diminished. Therefore, it was established that a case of CS can mimic ARVC as a clinical phenotype, and the specificity of the diagnostic criteria of ARVC is not sufficient in itself. Moreover, the CS diagnosis guide is mainly based on left ventricular dysfunction, and hence, CS, which is atypically predominant in the right ventricle, is difficult to diagnose.

　Therefore, several questions regarding the diagnostic criteria of ARVC and CS should be discussed to avoid misdiagnosis of these diseases.