Successful Treatment of Acrodermatitis Continua of Hallopeau with an Anti-IL-17A Agent.

Sir,

Acrodermatitis continua of Hallopeau (ACH) is characterized by pustules and atrophic skin changes in the tip of digits, onychodystrophy, and occasional osteolysis. ACH runs a chronic and relapsing course and may evolve into generalized pustular psoriasis (GPP). The disease is often refractory to various treatments and the effectiveness of biologics, such as anti-tumor necrosis factor-α, anti-interleukin (IL)-17A, and anti-IL-12/23 agents, has been reported.[123] However, the reports mentioning the efficacy of biologics are quite limited. We report here a case of ACH who has been treated successfully with anti-IL-17A agent.

A 15-year-old female presented with a 6-month history of severe scaly, erythematous, and pustular eruption on the nails, tip of digits, palms, and soles [Figure 1a]. A biopsy from the heel on histopathology showed hyperkeratosis, parakeratosis, cavities filled with neutrophils in stratum corneum, acanthosis with regular elongation of rete ridges, and lymphohistiocytic infiltrate around the vessels in the upper dermis [Figure 1b]. We emphasized the persistent subungual pustules and made the diagnosis of ACH according to the newly offered diagnostic criteria by European Rare and Severe Psoriasis Expert Network (ERASPEN).[4] Cyclosporine (CyA) in the dose of 3 mg/kg/day brought a dramatic improvement in 2 weeks. However, when the dose of CyA was decreased to 2 mg/kg/day, her disease rapidly worsened. As the increase of the dose of CyA to 3 mg/kg/day for 8 weeks did not improve her disease, we started the treatment with adalimumab. Administration of 80 mg of adalimumab was continued every 2 weeks for 16 weeks resulting in only subtle improvement. The patient was then put on subcutaneous administration of 300 mg secukinumab every 4 weeks and it demonstrated an excellent response in 8 weeks [Figure 1c]. Her disease has been well controlled for 8 months under secukinumab treatment.

Figure 1

(a) Severe scaly, erythematous, and pustular eruption on the nails, tip of digits, and the soles. (b) Hematoxylin–eosin (H–E) staining of the heel showed hyperkeratosis, dyskeratosis, cavities filled with neutrophils in stratum corneum, acanthosis with regular elongation of rete ridges, and lymphohistiocytic infiltrate around the vessels in the upper dermis (top: ×100, bottom: ×200). (c) Dramatic improvement after 8 weeks of secukinumab treatment

The diagnosis of ACH is in many cases controversial due to the discordance of clinical description among standard dermatology textbooks. The ERASPEN group stated a consensus classification of pustular psoriasis in order to make phenotypically well-matched disease groups for further clinical studies.[4] According to this classification, pustular psoriasis is classified into three groups: GPP, palmoplantar pustulosis, and ACH. A recent study also demonstrated the concurrence of psoriasis vulgaris in 46.2% of ACH based on the diagnostic criteria by the ERASPEN group and still mutations in IL-36 receptor antagonist gene were detected in ACH population.[5] Although our case can also be categorized as palmoplantar psoriasis, considering subungual continuous pustules, we regarded it reasonable to diagnose this case as ACH. Further standardization of diagnosis will help understand the disease pathogenesis.

Involvement of IL-17A in the pathogenesis of pustular psoriasis is well recognized and both innate and adaptive immune cells, such as neutrophils, macrophages, γδT cells, and Th17 cells, are regarded to contribute to IL-17A-enriched condition in the lesion of pustular psoriasis. Even with the dominance of IL-17A, however, the efficacy of anti-IL-17A agents on pustular psoriasis, especially ACH, is not established firmly. Anti-IL-17A agents can be good candidates for the treatment of ACH and further reports will be awaited.

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Conflicts of interest

There are no conflicts of interest.