IFN-a: interferon alfa LTT: lymphocyte transportation test TNF-a: tumor necrosis factorealfa T umor necrosis factor alfa (TNF-a) antagonists are commonly used to treat inflammatory disorders and are considered particularly effective in the treatment of moderate to severe psoriasis. Paradoxically, however, new-onset occurrence orworsening of psoriasis has been increasingly recognized among patients treated with TNF-a antagonists. We report on a 60-year-old man who developed a severe psoriatic condition with diffuse alopecia during infliximab therapy for psoriasis, resulting in the discontinuation of infliximab. Lymphocyte transportation test (LTT) results were positive. Currently, there are few reports of LTTpositive cases that are related to paradoxical reactions by TNF-a antagonists. We discuss the relationship between paradoxical reaction and the mechanisms of LTT.