In recent years, studies have associated dupilumab with unmasking or progression of cutaneous T‐cell lymphoma (CTCL). The objective of this study was to synthesize reported cases of CTCL in the setting of dupilumab use. Two independent reviewers conducted a systematic review using PubMed and Embase databases. Twelve studies, of 27 total patients, were included. Dupilumab‐associated CTCL was diagnosed on average 7.8 months following dupilumab initiation. Of reports that included body surface area (BSA), 100% had a BSA >50% prior to diagnosis, and the majority of patients were diagnosed at later stages of disease: stage III (4/18) or IV (6/18). Post‐dupilumab biopsies revealed a greater density of cells and a predominant lichenoid pattern, compared to various histologic patterns and less cell density in pre‐dupilumab biopsies. The majority of TCR gene rearrangement studies were equivocal (20%) or negative (60%), posing a potential diagnostic pitfall. Limitations included lack of standardized data collection and reporting and a small number of studies. We suggest that earlier biopsies, three to four months after initiation of dupilumab, may be helpful for earlier recognition of CTCL in patients who are not improving, progressing, or have morphologic changes on dupilumab.

Dupilumab is a humanized IgG4 monoclonal-antibody that is approved by the United States Food and Drug Administration (FDA) for the treatment of moderate-to-severe atopic dermatitis (AD) in patients aged 12 years and older. In recent years, several case studies have associated the unmasking or progression of cutaneous T-cell lymphomas (CTCL) with dupilumab treatment. To date, all reported cases of dupilumab-associated CTCL have shown a CD4+ T-helper-cell-predominant immunophenotype. Here, we report a case of a 72-year-old man who presented with a 2-year history of a diffuse, pruritic eruption, who was started on dupilumab for 9 weeks. He subsequently developed mycosis fungoides (MF) with a CD8+-predominant immunophenotype. Overall, cases of CD8+ mycosis fungoides are less common and relatively less understood than their CD4+ counterparts, with varied presentations and courses. We present a case of dupilumab-associated CD8+ MF to highlight this presentation for pathologists and providers.