Pustular psoriasis is an unusual form of psoriasis that frequently presents clinical challenges for dermatologists. The condition presents with pustules on an erythematous background and has two distinct subtypes: localized disease on the palms and soles, called palmoplantar pustulosis (PPP), and generalized pustular psoriasis (GPP). The involvement of the fingers, toes, and nails is defined as a separate localized variant, acrodermatitis continua of Hallopeau, and is now thought to be a subset of PPP. The rarity of pustular psoriasis frequently makes the correct diagnosis problematic. In addition, treatment is limited by a relative lack of evidence-based therapeutic options. Current management is often based on existing therapies for standard plaque psoriasis. However, there remains a need for treatments with high, sustained efficacy and a rapid onset of action in pustular psoriasis. Recent advances in understanding of the pathogenesis of pustular psoriasis have provided insights into potential therapies. Treatment of pustular psoriasis is generally determined by the extent and severity of disease, and recent years have seen an increasing use of newer agents, including biologic therapies. Current classes of biologic therapies with US Food and Drug Administration and European Medicines Agency approval for treatment of moderate-to-severe plaque psoriasis in the USA (and elsewhere) include tumor necrosis factor alpha inhibitors (adalimumab, certolizumab pegol, etanercept, infliximab), interleukin (IL)-17 inhibitors (brodalumab, ixekizumab, secukinumab), an IL-12/23 inhibitor (ustekinumab), and IL-23 inhibitors (guselkumab, risankizumab, tildrakizumab). Recently, specific inhibitors of the IL-36 pathway have been evaluated in GPP and PPP, including spesolimab, an IL-36 receptor inhibitor which has shown promising results in GPP. The emerging drugs for pustular psoriasis offer the possibility of rapid and effective treatment with lower toxicities than existing therapies. Further research into agents acting on the IL-36 pathway and other targeted therapies has the potential to transform the future treatment of patients with pustular psoriasis. This article reviews the clinical features of PPP and GPP, and current understanding of the genetics and immunopathology of these conditions; it also provides an update on emerging treatments.
Pustular psoriasis is a skin condition where people develop small pus-filled blisters on their skin. Pustular psoriasis may affect certain areas of the body, such as the palms and/or the soles. This is called palmoplantar pustulosis (PPP for short). Another type of pustular psoriasis can affect most of the body called generalized pustular psoriasis (GPP for short). Not many people have PPP or GPP. Around 5–12 in every 10,000 people worldwide develop PPP. GPP is even rarer, affecting only 2–7 out of every 1 million people. In addition to being relatively uncommon, these conditions are challenging to treat. This article aims to help doctors who treat skin conditions (dermatologists) to identify and treat people with pustular psoriasis. Currently there is no standard treatment for GPP and PPP in the USA or Europe, but several medicines are approved for treatment of GPP in Japan. Doctors often use treatments that have been shown to work in plaque psoriasis, which is the most common type of psoriasis, to treat people with GPP and PPP. Traditional treatments for PPP and GPP are often not effective. Researchers are working on developing new effective treatments for pustular psoriasis that may work more rapidly and have fewer side effects. These are expected to be available in the next few years.