ABSTRACT
BACKGROUND: Mogamulizumab (Mog) is a defucosylated, therapeutic monoclonal antibody, targeting CCR4 and was first approved in Japan for the treatment of adult T-cell leukaemia/lymphoma (ATLL), followed by cutaneous T-cell lymphoma and peripheral T-cell lymphoma. OBJECTIVE: To retrospectively investigate development of photosensitivity in patients with mycosis fungoides and other T-cell neoplasms after treatment with Mog. METHODS: We treated seven cutaneous lymphoma patients with Mog. Upon combination treatment with narrow-band UVB, we noticed that four patients developed photosensitivity dermatitis following Mog therapy, including two cases of mycosis fungoides, one case of adult T-cell leukaemia/lymphoma and one case of EB virus-associated T-cell lymphoproliferative disorder. Phototest was performed with UVA and UVB, and immunohistochemical staining for CD4, CD8 and Foxp3 was conducted in both photosensitivity and lymphoma lesions. RESULTS: Phototest revealed that the action spectrum of the photosensitivity was UVB in three cases and both UVB and UVA in one case. Histopathologically, the photosensitive lesions were characterized by a lichenoid tissue reaction with a CD8+ T cell-dominant infiltrate, sharing the feature with chronic actinic dermatitis, an autoreactive photodermatosis with a cytotoxic T-cell response. Foxp3+ regulatory T cells (Tregs) were decreased in the photosensitivity lesions compared with the lymphoma lesions. CONCLUSION: Increased incidence of photosensitivity reaction was observed during Mog treatment. Decreased number of Tregs in the lesional skin suggests that this reaction is possibly induced by autoreactive cytotoxic T cells.
