Acrodermatitis continua of Hallopeau successfully treated with bimekizumab: A case report

Introduction

Pustular psoriasis is an uncommon variant of psoriasis that is genetically and clinically distinct from psoriasis vulgaris. Pustular psoriasis is characterized by the presence of sterile pustules on an erythematous base and has several clinical presentations in either a localized or a generalized distribution.^1,2 Acrodermatitis continua of Hallopeau (ACH) is a rare form of localized pustular psoriasis that presents as a chronic, inflammatory, and relapsing eruption of sterile pustules on the distal fingers and sometimes toes, as well as the nail apparatus.^3,4 Pustules of the nail bed and matrix can lead to complications such as onychodystrophy, progressive destruction of the nail apparatus, and osteolysis.^3,4 Due to the chronic and relapsing nature of ACH, long-term control is needed to prevent these adverse outcomes.

Although pustular psoriasis shares clinical and histopathologic features with plaque psoriasis, this condition does not respond predictably to conventional psoriasis treatments, making it exceptionally challenging to manage. ³ In addition, no management guidelines exist, and there is a lack of data for and access to safe, effective, and durable therapies. ⁵ Different topical and systemic antipsoriatic therapies have been trialed based on the findings of case reports; however, efficacy is unclear and relapses are common.^3,6 Patients who fail to improve following traditional systemic therapies often initiate biologic therapy; however, data on their effectiveness for treatment of pustular psoriasis are limited.^1,5

We present a case of a patient with an 8-year history of ACH resulting in bilateral thumbnail destruction who was successfully treated with the biologic bimekizumab, after failing treatment with conventional psoriasis therapies.

Case report

A 25-year-old male presented in August 2021 with pustular psoriasis of the bilateral thumbnails resulting in onychodystrophy, proximal and lateral nail fold erythema, and tenderness. He reported an 8-year history of plaque psoriasis localized to the arms, axilla, groin, and gluteal cleft, with a remote history of acitretin treatment. The remainder of his medical history was negative and he was not on any medications. He reported no family history of psoriasis or related autoimmune conditions. His review of systems was unremarkable. A clinical diagnosis of ACH was made at the time of presentation.

Initial treatments between August 2021 and July 2022 included topical calcipotriene and betamethasone dipropionate foam, as well as the systemic agents acitretin and methotrexate which demonstrated a minimal benefit (Table 1). His disease course was complicated by a Staphylococcus aureus superinfection which was managed with intravenous (IV) ceftriaxone and doxycycline followed by oral cefalexin. In July 2022, the patient started bimekizumab treatment 320 mg every 4 weeks. He reported an excellent response and no adverse effects within the first week of bimekizumab treatment, and both thumbnails had regrown normally after 2 months (Figure 1).

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Table 1.

Summary of treatments, dosage, and response during the case report.

Date	Treatment and dosage	Response
August 2021	Topical (calcipotriene and betamethasone dipropionate) OD for 3 months	Minimal response
November 2021	Acitretin 10 mg OD for 1 month	Minimal initial response, not sustained
February 2022	Methotrexate 20 mg weekly with 5 mg OD folic acid supplementation for 20 weeks	Minimal response
July 2022	Bimekizumab 320 mg SC every 4 weeks for 16 weeks, ongoing	Great response, currently sustained

OD: once daily; SC: subcutaneous.

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Figure 1.

Patient’s thumbs (a) before treatment with bimekizumab and (b) 8 weeks after initiation of bimekizumab.

Discussion

This case demonstrates the challenges associated with successful treatment of ACH. The documented use of traditional topical and systemic antipsoriatic treatments to manage ACH is primarily limited to data from case reports. ³ Typical therapies include topical treatments such as corticosteroids, calcineurin inhibitors, and calcipotriol as well as antipsoriatic systemic therapies such as retinoids, methotrexate, cyclosporin, tetracyclines, colchicine, and dapsone.^3,6 Patients with psoriasis resistant to these traditional therapies often trial a biologic medication targeting various cytokines such as tumor necrosis factor (TNF), interleukin (IL)-17, and IL-12/23. ¹

Although the precise pathophysiology of pustular psoriasis and ACH is poorly understood, there is speculation that development is influenced by a combination of environmental exposures, genetic, and immune system abnormalities. ⁷ In pustular psoriasis, there is dysregulation of IL-36, Th17, neutrophil, and keratinocyte-driven inflammatory pathways. ⁸ Due to the involvement of the innate immune system, novel therapies for psoriasis are focused on the modulation of these pathways by targeting several pro-inflammatory cytokines such as IL-17.^9,10 The serum and mRNA levels of the IL-17 cytokine family are significantly elevated in patients with pustular psoriasis compared to those with non-pustular disease.^9,11–13 As IL-17 cytokines are potent neutrophil chemotactic factors, their elevated levels are consistent with the observed increased neutrophil infiltration characteristic of pustular psoriasis. ¹³ Recently, biologics targeting IL-17 have been trialed as a potential treatment for ACH due to the central involvement of this cytokine in the inflammatory cascade and pathogenesis of pustular psoriasis. ¹² A review of the literature has identified case reports of ACH successfully treated with different IL-17 inhibitors such as brodalumab, secukinumab, and ixekizumab.^14–20 However, the role of IL-17 inhibition in the development of pustular psoriasis is not fully understood, and a case of “paradoxical” pustular psoriasis has been reported in a patient receiving secukinumab treatment for plaque psoriasis. ²¹

Bimekizumab, a monoclonal IgG1 antibody that acts as a selective inhibitor of both IL-17A and IL-17F, has been found be a safe and effective treatment for patients with moderate-to-severe plaque psoriasis, and is capable of achieving high rates of skin clearance when dosed every 4 or 8 weeks.^22–26 In patients with plaque psoriasis, bimekizumab treatment has been found to normalize levels of IL-36 and IL-8, in addition to IL-17A and IL-17F, to achieve concentrations comparable to levels in non-lesional skin. ²⁷ Furthermore, reduction in IL-36 and IL-8 expression was greater with bimekizumab compared to inhibitors of IL-17A or IL-17F alone. ²⁷

To date, no clinical trials or case reports/series have investigated the use of bimekizumab to treat pustular psoriasis or ACH. Our patient with bilateral thumbnail destruction due to his ACH experienced normal regrowth of both thumbnails following bimekizumab treatment. This case contributes to the current knowledge base for ACH and demonstrates the ability of the biologic bimekizumab to safely and effectively manage ACH which was recalcitrant to conventional antipsoriatic therapies. Furthermore, understanding of ACH and improved availability of treatment options is needed to successfully manage ACH in the future.