A Case of Psoriasis Verrucosa Successfully Treated With Adalimumab

Psoriasis verrucosa is a peculiar clinical form of psoriasis characterized by very thick and hard scales adherent to erythematous lesions, producing a wartlike appearance.¹ The case of a Japanese patient with psoriasis verrucosa that was successfully treated with adalimumab is herein described.

A 55-year-old Japanese male had a five-year history of psoriasis vulgaris treated with topical corticosteroids and a topical vitamin D₃ ointment. He also had atypical psychosis treated with lithium carbonate and mild obesity (body mass index 28 kg/m²). He had scaly erythema on the trunk and extremities, but verrucous scales on erythematous plaque developed three years ago (Figure 1). The biopsy specimen of verrucous lesions showed marked hyperkeratosis and parakeratosis with infiltrating neutrophils, severe papillomatosis with thinning of the granular layer, elongation and thickening of the rete ridges, and diffuse infiltration of lymphocytes into the upper dermis (Figure 2).

Immunohistochemical staining for the human papilloma virus protein was negative (polyclonal rabbit antibovine papillomavirus type 1 antibody; Dako, Glostrup, Denmark). Clinical and histopathological findings led to the diagnosis of psoriasis verrucosa. His mental condition prevented adequate treatment of the verrucous lesions. He had been receiving oral cyclosporine (3 mg/kg daily) for a year, although it showed little efficacy (Psoriasis Area and Severity Index [PASI] score 16.2). Adalimumab (40 mg every other week) was given for the skin eruption, and it showed remarkable efficacy in five months (PASI score 3.7; Figure 3).

Psoriasis verrucosa is a rare, atypical clinical form of psoriasis, featuring a wartlike appearance or a wartlike cracked surface. Psoriasis verrucosa commonly develops on the legs, palms, backs of the hands, soles, and ankles. Psoriasis verrucosa is associated with obesity, diabetes mellitus, and peripheral circulatory failure.¹ One possible explanation for why the reported case subject developed psoriasis verrucosa is that lithium carbonate inhibits adenylate cyclase and decreases cyclic adenosine monophosphate in keratinocytes. It inhibits the G2 block in cell cycle division and promotes keratinocyte turnover. Another hypothesis is that lithium carbonate and insufficient treatment may have promoted the development of psoriasis verrucosa. Oral etretinate is reported to be very effective for psoriasis verrucosa.^1-3 Adalimumab impacts dermal-based immunocytes, and the epidermal compartment also responds by restoration of normal differentiation.⁴ Increases in the mRNA levels of interleukin (IL)-1b, IL-8, IL-17c, and IL-20 in psoriatic skin have already been shown to be significantly reduced after adalimumab treatment.⁵ It has been pointed out that adalimumab reduces p38 mitogen-activated protein kinase (MAPK) phosphorylation, with a subsequent decrease in the expressions of p38 MAPK-regulated genes in patients with psoriasis.⁵ The present case of psoriasis verrucosa is the first to be successfully treated with adalimumab. Further studies are required to elucidate both the cause and the ideal treatment of this disease.