A Case of Palmoplantar Psoriasis Successfully Treated With Tapinarof Cream

Palmoplantar psoriasis is a difficult-to-treat psoriasis variant that affects the palms and soles [1]. Tapinarof, a topical aryl hydrocarbon receptor-modulating agent, is approved for the treatment of plaque psoriasis [2]. Herein, we report a case of palmoplantar psoriasis successfully treated with tapinarof cream. An 11-year-old boy was referred to our hospital with skin lesions on the palms and soles. Symptoms appeared 1 year before the initial visit. Physical examination revealed crusty erythema with fissures on the palms and soles (Figure 1a,b) and pale erythema on the elbows. Histopathological findings of the crusty erythema on the left sole showed parakeratosis, orthokeratosis, an elongated rete ridge, and lymphocyte exocytosis (Figure 1c,d). The patient was administered maxacalcitol, betamethasone butyrate propionate, and fludroxycortide tape. However, skin lesions were refractory to topical therapies and appeared on the face and knees at 13 years of age. The patient was treated with 150 mg of secukinumab (administered once weekly for 5 weeks, then every 4 weeks) for 6 months, followed by 300 mg of secukinumab every 4 weeks for 9 months. The skin lesions improved but a sufficient efficacy response was not observed, and secukinumab was discontinued. Skin lesions on the palms and soles remained unchanged (Figure 1e,f) and tapinarof cream was administered to the right sole at the age of 16 years. The skin lesions on the right sole gradually improved after 6 months of treatment (Figure 1g). Notably, erythema, scaling, and fissuring on the palms improved without treatment (Figure 1h). In Japanese patients with psoriasis, the most commonly affected region is the upper extremities excluding the hands and lower extremities excluding the feet, whereas the less common region is the hands and feet [3]. However, the palms and soles are recognized as recalcitrant regions of psoriasis, and systemic therapies, including biologic therapies, are considered even in patients with limited skin involvement in these regions [4]. Recently, various biologic therapies have become available, and secukinumab is only approved for children and adolescents aged ≥ 6 years. In addition, secukinumab provides a strong and sustained response for > 2.5 years in difficult-to-treat palmoplantar psoriasis [5]. However, in the present case, skin lesions of the palms and soles were refractory to secukinumab. Limited data are available on the treatment of palmoplantar psoriasis, and no standardized treatment exists [1]. Although tapinarof is a newly available topical agent for psoriasis treatment, no studies have explored its efficacy in palmoplantar psoriasis. In the present case, the efficacy response was observed gradually in the region of application of tapinarof cream. Notably, a response was also observed in anatomically distant nonapplied regions. This may be attributed to percutaneous absorption, leading to systemic circulation of tapinarof, which can be observed in some patients. However, systemic adverse events, such as headache and pyrexia were not observed. A total of 45 g of tapinarof cream was applied to the right sole in the 6 months. Pharmacokinetics (distribution and metabolism) of tapinarof cream remain to be fully elucidated. Further investigation is needed to clarify the exact pharmacological action of tapinarof cream. The authors have nothing to report. The authors have nothing to report. The authors have nothing to report. The authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request.