{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T17:17:02Z","timestamp":1790615822526,"version":"4.1.0"},"reference-count":16,"publisher":"BMJ","issue":"9","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Case Rep"],"accepted":{"date-parts":[[2026,9,7]]},"published-print":{"date-parts":[[2026,9]]},"abstract":"<jats:p>Atopic dermatitis and cutaneous T-cell lymphoma can overlap both clinically and histopathologically, potentially delaying recognition of early disease. We report a case of a woman in her 40s with longstanding atopic diathesis who developed patch-stage mycosis fungoides after more than 5 years of stability on dupilumab. Earlier biopsies showed spongiotic dermatitis without evidence of a lymphoproliferative disorder. She later presented with a rapidly progressive, intensely pruritic eruption of erythematous scaly plaques with near-erythroderma, morphologically distinct from her prior dermatitis. Repeat biopsy revealed an epidermotropic atypical lymphoid infiltrate consistent with mycosis fungoides. This case highlights the importance of reassessment in patients with presumed atopic dermatitis who develop atypical features, rapid progression or diminished response to therapy. It also raises the possibility that dupilumab may unmask previously unrecognised cutaneous T-cell lymphoma in some patients and highlights the need for further study of interleukin-4 and interleukin-13 pathway modulation.<\/jats:p>","DOI":"10.1136\/bcr-2026-272281","type":"journal-article","created":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T16:31:05Z","timestamp":1790613065000},"page":"e272281","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Cutaneous T-cell lymphoma emerging during long-term dupilumab therapy in a patient with longstanding atopic diathesis: diagnostic challenges and mechanistic considerations"],"prefix":"10.1136","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-6463-2004","authenticated-orcid":false,"given":"Samantha","family":"Mills","sequence":"first","affiliation":[{"name":"Medical School, Campbell University Jerry M Wallace School of Osteopathic Medicine, Lillington, North Carolina, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ryan","family":"Geist","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Campbell University, Buies Creek, North Carolina, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Phuong","family":"Daniels","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Campbell University, Buies Creek, North Carolina, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jonathan","family":"Crane","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Campbell University, Buies Creek, North Carolina, USA"},{"name":"Sampson Regional Medical Center, Clinton, North Carolina, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2026,9,28]]},"reference":[{"key":"2026092809301312000_19.9.e272281.1","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1053\/j.semdp.2016.11.001","article-title":"Mycosis fungoides and S\u00e9zary syndrome","volume":"34","author":"Cerroni","year":"2017","journal-title":"Semin Diagn Pathol"},{"key":"2026092809301312000_19.9.e272281.2","doi-asserted-by":"publisher","DOI":"10.1182\/blood-2018-11-881268"},{"key":"2026092809301312000_19.9.e272281.3","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa1610020"},{"key":"2026092809301312000_19.9.e272281.4","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(17)31191-1"},{"key":"2026092809301312000_19.9.e272281.5","doi-asserted-by":"crossref","first-page":"197","DOI":"10.1016\/j.jaad.2020.03.050","article-title":"Progression of cutaneous T-cell lymphoma after dupilumab therapy","volume":"83","author":"Espinosa","year":"2020","journal-title":"J Am Acad Dermatol"},{"key":"2026092809301312000_19.9.e272281.6","first-page":"166","article-title":"Psoriasis dermatitis: a new entity or a different phenotypic expression of psoriasis and atopic dermatitis?","volume":"159","author":"Bardazzi","year":"2024","journal-title":"Ital J Dermatol Venerol"},{"key":"2026092809301312000_19.9.e272281.7","doi-asserted-by":"crossref","DOI":"10.3390\/jcm13061603","article-title":"Atypical Manifestations of Syphilis: A 10-Year Retrospective Study","volume":"13","author":"Ciccarese","year":"2024","journal-title":"J Clin Med"},{"key":"2026092809301312000_19.9.e272281.8","doi-asserted-by":"crossref","first-page":"255","DOI":"10.1016\/j.jaad.2024.03.039","article-title":"Dupilumab therapy for atopic dermatitis is associated with increased risk of cutaneous T cell lymphoma: A retrospective cohort study","volume":"91","author":"Hasan","year":"2024","journal-title":"J Am Acad Dermatol"},{"key":"2026092809301312000_19.9.e272281.9","doi-asserted-by":"crossref","DOI":"10.1155\/2024\/9924306","article-title":"Increased Risk of Cutaneous T-Cell Lymphoma Development after Dupilumab Use for Atopic Dermatitis","volume":"2024","author":"Mandel","year":"2024","journal-title":"Dermatol Ther"},{"key":"2026092809301312000_19.9.e272281.10","doi-asserted-by":"crossref","unstructured":"Kridin K , Bieber K , Olbrich H , et al . Dupilumab treatment is not associated with changes in lymphoma risk in atopic dermatitis and other type 2 inflammatory diseases: data from a large-scale retrospective cohort study. Front Med (Lausanne) 2026.","DOI":"10.3389\/fmed.2025.1702736"},{"key":"2026092809301312000_19.9.e272281.11","doi-asserted-by":"crossref","unstructured":"Ma K , Brumbaugh B , Saff R , et al . Dupilumab and lymphoma risk among patients with asthma: a population-based cohort study. 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