症例は61歳男性。病歴11年の2型糖尿病患者。経口血糖降下薬を服薬していたがHbA1c 10％前後とコントロール不良であった。2ヵ月の内服自己中断後に糖尿病ケトアシドーシスのため緊急入院となった。インスリン療法を開始し，第7病日よりリラグルチドに変更した。第14病日よりエキセナチドに切り替えた。患者には15年来の尋常性乾癬があったが，GLP-1受容体作動薬開始後より乾癬による掻痒感，皮疹は改善した。以前インスリン療法により血糖コントロールが改善した際も，乾癬による掻痒感は改善しなかったことから，GLP-1受容体作動薬の作用による可能性も示唆された。GLP-1受容体作動薬が乾癬に有効であるとする報告は，海外にいくつかあるもののわれわれの調べた範囲では国内での報告を認めない。今回尋常性乾癬を合併した2型糖尿病において，GLP-1受容体作動薬開始後より乾癬の改善を認めた症例を経験したため報告する。

   A 61-year-old man had type 2 diabetes mellitus for 11 years. He was treated with oral hypoglycemic agents; however, his glycated hemoglobin (HbA1c) level was ~10％. After self-interrupting his medication for 2 months, he was admitted to our hospital on an emergent basis owing to diabetic ketoacidosis. Intensive insulin therapy was applied, followed by liraglutide instead of insulin on the seventh hospital day and exenatide on the 14th hospital day. The patient had been diagnosed with psoriasis vulgaris 15 years previously. Symptoms of psoriasis, such as itching and skin eruptions, significantly improved after the initiation of glucagon-like peptide-1 (GLP-1) receptor agonist treatment. Previously, when he had achieved good glycemic control with insulin therapy, itching from the psoriasis remained unchanged. We speculated that the improvement in psoriasis may have been independent of glycemic control and dependent on the effects of the GLP-1 receptor agonist. Recently, several reports from the United States and Europe suggest that the GLP-1 receptor agonist is effective for psoriasis in patients with type 2 diabetes, but there are few such reports in Japan. We report a case of type 2 diabetes who demonstrated improvement in psoriasis after the initiation of GLP-1 receptor agonist therapy.