イキセキズマブ投与中に発症した潰瘍性大腸炎様大腸炎の1例

A Case of UC-like Colitis Developing During Ixekizumab Therapy

要旨●患者は尋常性乾癬に対しイキセキズマブを投与中の40歳代，男性．イキセキズマブ投与15か月後に下痢・下血を呈した．直腸優位の左側結腸に潰瘍性大腸炎（UC）様の内視鏡所見と炎症性変化（陰窩膿瘍，杯細胞の減少など）を認めた．イキセキズマブ中止のみで症状および内視鏡所見は速やかに改善し，代替として抗IL-23p19抗体製剤へ変更後，4年間再燃を認めなかった．IL-17阻害薬関連腸炎はまれであるが，下痢・血便出現時には感染性腸炎の除外と早期の内視鏡評価が重要である．

　A man in his 40s receiving ixekizumab for plaque psoriasis experienced diarrhea and hematochezia 15 months after treatment initiation. Endoscopic examination revealed ulcerative colitis-like findings predominantly in the rectum and left-sided colon, accompanied by inflammatory changes such as crypt abscesses and decreased goblet cells. Discontinuation of ixekizumab alone led to rapid improvement in symptoms and endoscopic abnormalities. After switching to an anti-IL‐23p19 antibody as an alternative therapy, he remained relapse-free for 4 years. Although IL‐17 inhibitor-associated colitis is rare, the exclusion of infectious enterocolitis and prompt endoscopic evaluation are essential when patients present with diarrhea or bloody stools.