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Successful treatment of CCR4+ mycosis fungoides palmaris et plantaris with mogamulizumab monotherapy

Dear Editor, Mycosis fungoides palmaris et plantaris (MFPP) is a rare variant of MF limited to the palms and soles that presents with a relatively good prognosis. On the other hand, MFPP with large cell transformation that required the administration of systemic chemotherapy has been reported, suggesting that MFPP could progress to the tumor stage. A 67-year-old Japanese man visited our outpatient clinic with a 3-year history of hyperkeratotic erythema on the palm and erythematous plaque on the extremities. On his initial visit, physical examination revealed hyperkeratotic, well-demarcated scaly erythema limited on bilateral palms (Figure 1A) and soles. A biopsy specimen from the left palm revealed dense infiltration of atypical lymphocytes with epidermotropism in the superficial dermis (Figure 1B) and deep dermis (Figure 1C). Immunohistochemical staining showed that these atypical lymphocytes were positive for CD2, CD3, CD4, and CCR4 (Figure 1D, E) and negative for CD7, CD8, and CD30. A biochemical profile revealed a significantly high level of serum soluble IL-2 receptor (734 U/ mL) and Lactate Dehydrogenase (LDH) (299 U/L). Computed tomography showed no evidence of lymph node swelling or visceral lesions. Given the above-mentioned findings, the diagnosis was MFPP (T3N0M0B0 stage IIb). The patient was treated with mogamulizumab 1 mg/kg/week for 4 weeks and subsequently with mogamulizumab 1 mg/kg/2 weeks. The lesional skin of the palmoplantar area gradually decreased (Figure 1F), and 4 months after the initial administration of mogamulizumab, he had achieved complete remission. Since the serum CCL22 level has been reported as a biomarker for disease activity, we evaluated the serum CCL22 as well as CCL19 and CXCL10 before and 1 month after the administration of mogamulizumab. The serum levels of CCL22 decreased in parallel with the disease activity, whereas there was no difference in the serum CCL19 and CXCL10 (Figure 2). Since MFPP is mainly located at the palms and sole areas, the majority of therapies for MFPP are local therapy. On the other hand, the successful treatment with several systemic therapies combined with local therapies has also been reported. Miernik et al reported that oral bexarotene in combination with ultraviolet B (UVB) therapy