Background and importance Sezary syndrome (SS) is a primary cutaneous T cell lymphoma characterised by erythroderma, lymphadenopathy and leukaemic involvement of the peripheral blood. The high relapse rates and poor prognosis complicate its clinical course and treatment. Mogamulizumab is an anti-CC chemokine receptor 4 monoclonal antibody that has been recently approved for the treatment of adult patients with relapsed or refractory mycosis fungoides or SS who have been treated with at least one prior line of therapy.

Aim and objectives To describe the use of mogamulizumab in a patient with SS as well as the safety of this new treatment.

Material and methods We ran a descriptive study of SS in a 77-year-old woman with erythema for 8 years. Skin lesions were widely distributed over 80% of her body. The patient was initially diagnosed with contact dermatitis and then psoriasis. She received various treatments without success: antihistamines, topical corticosteroids, acitretin, cyclosporine, oral prednisone, phototherapy, ustekinumab, ixekizumab, methotrexate and bexarotene. In June 2020, due to new recurrences, additional skin biopsy and study of bone marrow were done to determine the specific type of skin lesions. Stage IV SS (pT4pM0pN0 B2) was diagnosed, and physicians decided to start expanded access treatment with mogamulizumab.

Results The patient received eight doses (80 mg/dose) of mogamulizumab from June to October 2020. It was administered with the approved protocol: 1 mg/kg dose, as an intravenous infusion over at least 60 minutes, on days 1, 8, 15, and 22 of the first 28 day cycle, then on days 1 and 15 of each subsequent 28 day cycle until disease progression or unacceptable toxicity. The woman presented good clinical evolution with reduction of skin lesions and symptoms. The treatment was well tolerated, with few reported adverse side effects: low grade fever after the first infusion and grade IV afebrile neutropenia after the sixth dose. Severe neutropenia was successfully treated with granulocyte colony stimulating factors and the patient was able to continue treatment.

Conclusion and relevance Mogamulizumab was used successfully to date in our case. Although more and longer treatment periods are needed, mogamulizumab seems to be a well tolerated treatment option for SS.

Conflict of interest No conflict of interest