Introduction

Generalized Pustular Psoriasis (GPP) is a subtype of pustular psoriasis, a group of inflammatory skin conditions characterized by infiltration of neutrophil granulocytes in the epidermis, that can present as an acute, subacute, or chronic pustular eruption on erythematous non-acral skin. According to the European Rare and Severe Psoriasis Expert Network (ERASPEN), GPP can occur with or without systemic inflammation, with or without psoriasis vulgaris and can either be a relapsing (>1 episode) or persistent (>3 months) condition [1]. The exact pathogenesis of this condition has not been fully understood. However, the evidence of sustained activation of IL-1 and IL-36 in GPP suggests that the IL-1/IL-36 inflammatory axis plays a key role [2]. In addition, in several patients with GPP has been detected the mutations in the IL36RN gene that encodes the interleukin-36 receptor antagonist (IL-36Ra), an anti-inflammatory cytokine in the IL-1 family [3]. The resulting upregulation of IL-36 activity promotes CD4+ T-cells proliferation with increased production of lL-17A, which represents a key mediator in GPP, such as in plaque psoriasis [4]. Given the rarity of this disease, there are no standardized guidelines for the treatment of GPP with biologics, in patients with contraindications or inadequate response to conventional immunosuppressive therapies.

Case Report

We report the case of a 56-year-old patient, who came to our attention reporting a 10-year history of psoriasis vulgaris. In the past, he had been treated with topical corticosteroids and UVB narrow band phototherapy, with only partial and temporary improvement. He had also a history of hypertension and type 2 diabetes mellitus. In 2013 he had a myocardial infarction, treated with angioplasty, and in 2019 he received antiviral therapy after the detection of hepatitis C infection, with subsequent viral eradication. The patient came to our attention with erythematous plaques covered with severe scales on all four limbs. On the back, the patient exhibited several erythematous patches, surrounded by barely perceptible papules and pustules, all covered with excoriating crusts (Figure 1a-b).

Figure 1: a, b) Erythematous patches with mild scaling and some pustule on the back of a 56-year-old patient with a close-up of some cutaneous lesion on the upper back.

Erythematous patches, along with some pustules and scales, were also observed on the forehead (Figure 1c).

Figure 1: c) Erythema and pustule on the forehead of the patient.

The patient reported the appearance of these cutaneous lesions a month before and he recalled similar episodes during the past years. In the clinical suspicion of a GPP flare superimposed on plaque psoriasis, we performed a skin biopsy and prescribed the screening panel in the prevision of treatment with biologic drugs. The histopathology report described the presence of moderate acanthosis of the epidermis with ortho-parakeratosis, neutrophils, micro-pustules and superficial erosions; in the dermis, superficial mixed inflammatory infiltrates with the prevalent load on the papillary dermis (Figure 2, b).