肺の日和見感染症の画像診断

Radiologic findings of opportunistic infections

今日では，化学療法や免疫抑制剤使用，ステロイド長期投与，後天性免疫不全症候群（acquired immunodeficiency syndrome：AIDS）など様々な要因による免疫低下患者が多くみられる。免疫低下患者が発症する日和見感染症は臨床的に問題となり，画像診断の果たす役割は大きい。本稿では，日和見感染症の中でも重要なニューモシスチス肺炎，サイトメガロウイルス肺炎，肺アスペルギルス症について述べる。また，抗ヒト免疫不全ウイルス（human immunodeficieny virus：HIV）療法開始後に生じる免疫再構築症候群についても概説する。

In pneumocystis pneumonia, ground-glass attenuation predominantly in the upper lobes is seen on CT. In AIDS patients, cyst formation predominantly in the upper lobe is sometimes observed. Compared with AIDS patients, non-AIDS patients have more extensive ground-glass attenuation, more frequent consolidations, and more rapid progression. Cytomegalovirus pneumonia shows multiple nodules in addition to extensive ground-grass attenuation. CT halo sign is often observed in vascular invasive aspergillosis. However, these findings may also be observed in other diseases, and it is sometimes difficult to diagnose accurately based on CT findings alone.