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Original Investigation
April 21, 2021

Clinical Characterization of Mogamulizumab-Associated Rash During Treatment of Mycosis Fungoides or Sézary Syndrome

Author Affiliations
  • 1Department of Dermatology, Stanford University School of Medicine, Palo Alto, California
  • 2Department of Pathology, Stanford University School of Medicine, Stanford, California
  • 3Division of Oncology, Department of Medicine, Stanford University School of Medicine, Stanford, California
JAMA Dermatol. Published online April 21, 2021. doi:10.1001/jamadermatol.2021.0877
Key Points

Question  What are the clinical features of mogamulizumab-associated rash (MAR) during treatment of mycosis fungoides (MF) and Sézary syndrome (SS)?

Findings  In this retrospective case series, MAR exhibited heterogeneous features that often clinically mimicked cutaneous MF or SS; in addition, MAR had a predilection for the head and neck and demonstrated 4 predominant patterns: folliculotropic MF–like scalp plaques with alopecia, papules and/or plaques, photoaccentuated dermatitis, and morbilliform dermatitis, and histopathologic patterns were variable. Ancillary testing (immunohistochemistry and T-cell clonality studies) can help differentiate MAR from disease.

Meaning  Distinguishing MAR from cutaneous MF or SS is essential but difficult because clinical and histopathologic features can be variable in MAR.


Importance  Mogamulizumab is a monoclonal antibody against CCR4 approved for treatment for mycosis fungoides (MF) and Sézary syndrome (SS). Mogamulizumab-associated rash (MAR) is difficult to differentiate from cutaneous MF or SS, which can lead to unnecessary discontinuation of drug use because of concern for severe drug reaction or incorrect presumption of disease relapse or progression in the skin.

Objective  To examine the most common clinical presentations of MAR in patients with MF or SS and the diagnostic and management challenges.

Design, Setting, and Participants  This retrospective case series assessed patients from a multidisciplinary cutaneous lymphoma clinic and supportive oncodermatology clinic at a major academic referral center who had a diagnosis of MF or SS and received mogamulizumab from January 1, 2013, to January 1, 2020. Treatment was followed by new or worsening rash with skin biopsy results compatible with drug eruption determined by clinicopathologic correlation and molecular testing to exclude active malignant disease.

Exposures  At least 1 dose of mogamulizumab.

Main Outcomes and Measures  Mogamulizumab-associated rash was characterized by clinical features, including time to onset, clinical presentation, histopathologic features, and management approach.

Results  The study included 19 patients with MF or SS who developed MAR (median age, 65 years; age range, 38-82 years; 10 [52.6%] male). Median time to MAR onset was 119 days (range, 56 days to 3.8 years). Patients with MAR exhibited 4 predominant clinical presentations: (1) folliculotropic MF–like scalp plaques with alopecia, (2) papules and/or plaques, (3) photoaccentuated dermatitis, and (4) morbilliform or erythrodermic dermatitis. The most common anatomical region involved was the head and neck, including the scalp. Histopathologic findings were variable and did not correspond to primary clinical morphologic findings. Immunohistochemistry and T-cell clonality ancillary testing were helpful to distinguish MAR from disease. Most patients with MAR (14 of 19) discontinued mogamulizumab treatment; however, no life-threatening severe cutaneous adverse drug reactions occurred, and the decision for drug therapy cessation was usually multifactorial. Four patients were treated again with mogamulizumab with no life-threatening drug-related events. Approaches to management of MAR include topical corticosteroids, systemic corticosteroids, and/or methotrexate.

Conclusions and Relevance  This case series found that mogamulizumab-associated rash had a heterogeneous clinical presentation with variable and delayed onset in patients with MF or SS. Mogamulizumab-associated rash exhibited a predilection for the head and neck and was difficult to clinically distinguish from relapse or progression of disease. Recognition of the most common clinical presentations can help prevent unnecessary discontinuation of mogamulizumab treatment. The presence of MAR does not necessitate permanent discontinuation of or avoidance of retreatment with mogamulizumab.

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