Dermatology: Practical and Conceptual Research Letter | Dermatol Pract Concept. 2025;15(3):5316 1 Efficacy of Bimekizumab in the Management of Refractory Erythrodermic Pityriasis Rubra Pilaris: Clinical Insights Sofia Theotokoglou1, Dimitrios Sgouros1, Konstantinos Theodoropoulos1, Anna Syrmali1, Georgia Pappa1, Alexandros Katoulis1 1 2nd Department of Dermatology and Venereology, National and Kapodistrian University of Athens, Medical School, “Attikon” General University Hospital, Athens, Greece Key words: Erythroderma, Bimekizumab, Pityriasis rubra pilaris, Refractory erythroderma treatment, Bimekizumab efficacy Citation: Theotokoglou S, Sgouros D, Theodoropoulos K, et al. Efficacy of Bimekizumab in the Management of Refractory Erythrodermic Pityriasis Rubra Pilaris: Clinical Insights. Dermatol Pract Concept. 2025;15(3):5316. DOI: https://doi.org/10.5826/dpc.1503a5316 Accepted: January 21, 2025; Published: July 2025 Copyright: ©2025 Theotokoglou et al. This is an open-access article distributed under the terms of the Creative Commons Attribution- NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing Interests: None. Authorship: All authors have contributed significantly to this publication. Corresponding Author: Georgia Pappa, “Attikon” General University Hospital, 2nd Dept. of Dermatology-Venereology, Athens, Greece. E-mail: gpappa100@gmail.com Introduction Erythroderma refers to widespread skin reddening caused by inflammatory dermatoses, with pityriasis rubra pilaris (PRP) being a notable cause. While PRP can sometimes resolve spontaneously, erythroderma requires prompt treatment, often posing a challenge. Traditional therapies like cortico- steroids, retinoids, immunosuppressants, and phototherapy have shown limited efficacy [1]. Though no biologics are of- ficially approved for PRP, IL-17, IL-12/23, and IL-23 inhibi- tors are increasingly used [1-3]. Elevated IL-17A and IL-17F levels in PRP suggest bimekizumab, a biologic targeting both, as a promising option [4]. We herein present a case demon- strating its potential effectiveness in PRP management. Case Presentation A 42-year-old white male presented with widespread ery- thema that had begun three months earlier as fine scaling and redness on the scalp. He reported mild pruritus, without fever or other systemic symptoms. His medical history was unremarkable, and there was no family history of skin dis- eases. Physical examination revealed a pink-red-to-salmon- colored erythroderma with a fine epidermal scale, which was thicker and more adherent on the face and scalp. The involved skin was sharply demarcated from the adjacent un- involved skin, creating “islands of sparing,” a hallmark of PRP (Figure 1). Moderate palmoplantar keratoderma was noted, without onychodystrophy, lymphadenopathy, or or- ganomegaly. A prior dermatology consultation, including a skin biopsy, had led to treatment with topical corticosteroids and emollients, with no improvement. Laboratory workup, including CBC, CRP, ESR, and tests for hepatitis B, C, and HIV, was unremarkable. Lupus erythematosus was ex- cluded by normal complement levels and negative ANA and anti-dsDNA tests. Flow cytometry was performed to rule out cutaneous lymphomas. To control the erythroderma the pa- tient was initially administered methylprednisolone 60 mg 2 Research Letter | Dermatol Pract Concept. 2025;15(3):5316 daily (0.75 mg/kg twice a day). Skin histopathology revealed hyperkeratosis, parakeratosis, mild epidermal hyperplasia, spongiosis, and lymphocytic infiltration in the perivascular and upper dermis; findings consistent with PRP. After 10 days of corticosteroids with no improvement, acitretin 30 mg/day was initiated but proved ineffective af- ter one month. It was replaced with subcutaneous meth- otrexate 15 mg/week and folic acid 5 mg/week. Despite two months of methotrexate therapy, the patient showed no significant skin improvement. At this stage, it was de- cided to switch from conventional treatments to biologic therapy. With informed consent, bimekizumab was admin- istered at the psoriasis-approved dose (320 mg subcutane- ously at weeks 0, 4, 8, 12, and 16, then every eight weeks). Remarkably, near-complete remission of the skin rash was observed after just two doses at weeks 0 and 4 (Figure 2), while complete remission was achieved by the 4th dose. The patient has been on treatment for 11 months, with no signs of recurrence to date. Conclusion Although biologic agents are not officially indicated for PRP, they are increasingly used in severe, refractory cases, with ev- idence supporting the efficacy of IL-17A antagonists [3]. Bi- mekizumab, a newly approved biologic targeting IL-17A and IL-17F, is highly effective in psoriasis. To date, two published cases have reported successful PRP treatment with bimeki- zumab [5,6]. Unlike these cases, where longer disease duration may have influenced outcomes, our patient had a shorter dis- ease course and achieved near-complete remission after just two doses. While evidence suggests PRP responds variably to biologics, further studies are needed to assess bimekizumab effi- cacy and identify the optimal biologic treatment for PRP [1-6]. Figure 1. A 42-year-old male with (A-C) pink-to-salmon-colored erythroderma with distinct “islands of sparing” and (B) moderate orange-waxy palmoplantar keratoderma. Figure 2. The same patient five weeks after starting bimekizumab. (A-C) Near-complete remission of the skin rash is evident. Research Letter | Dermatol Pract Concept. 2025;15(3):5316 3 References 1. Kromer C, Sabat R, Celis D, et al. Systemic therapies of pityria- sis rubra pilaris: a systematic review. J Dtsch Dermatol Ges. 2019;17(3):243–259. DOI: 10.1111/ddg.13718. PMID: 30520557. 2. Kromer C, Schön MP, Mössner R. Treatment of pityriasis ru- bra pilaris with risankizumab in two cases. J Dtsch Dermatol Ges. 2021;19(8):1207–1209. DOI: 10.1111/ddg.14504. PMID: 33973380. 3. Napolitano M, Abeni D, Didona B. Biologics for pityriasis rubra pilaris treatment: a review of the literature. J Am Acad Dermatol. 2018;79(2):353–359.e11. DOI: 10.1016/j.jaad.2018.03.036. PMID: 29609014. 4. Feldmeyer L, Mylonas A, Demaria O, et al. Interleukin 23-Helper T Cell 17 Axis as a treatment target for pityriasis rubra pilaris. JAMA Dermatol. 2017;153(4):304–308. DOI: 10.1001/jama- dermatol.2016.5384. PMID: 28122069. 5. Saad M, Bose R. 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