乳房全切除術後の放射線治療により尋常性乾癬の増悪をきたした1例

A case of exacerbation of psoriasis vulgaris following postmastectomy radiation therapy

尋常性乾癬は慢性に軽快・増悪を繰り返す炎症性角化症の1つであり，肘頭，膝蓋，被髪頭部，臀部など刺激を受けやすい部位に厚い鱗屑を付着した紅斑局面を形成する原因不明の疾患である。一方,乳癌に対する乳房全切除術後の放射線治療は局所および領域リンパ節再発の予防，生存率の向上を目的に実施される一般的な治療であるが，放射線皮膚炎が問題になることがある。今回我々は，尋常性乾癬を有する患者に対する乳房全切除術後の放射線治療後に尋常性乾癬の再燃・増悪を経験したので報告する。

We present the case of a patient with a known history of psoriasis vulgaris, who experienced an exacerbation of both the irradiated and non-irradiated skin areas after postmastectomy radiation therapy（PMRT）. The patient, a woman in her 40s, had left breast cancer and underwent PMRT with a total dose of 42.5Gy in 16 fractions. Approximately one month after completing her radiation treatment, she developed patches of psoriasis vulgaris over the irradiated area. This is known as the Köbner phenomenon. With one-month topical ointment application, the psoriatic patch had significantly improved. This case highlights the importance of considering the Köbner phenomenon as an uncommon radiation skin reaction in patients with psoriasis vulgaris, even when the skin dose is relatively low.