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Generalised pustular psoriasis (GPP) is a rare, chronic, inflammatory skin disease that may manifest as a relapsing disease with recurrent flares or a persistent disease with intermittent flares. GPP is associated with a significant clinical burden, including pain, fatigue, and comorbidities, leading to severe, life-threatening complications. The frequency and severity of GPP flares have not been characterised comprehensively in epidemiological studies. Comprehensive literature searches were conducted to identify studies evaluating mortality, prevalence, comorbidities, and flares in the GPP population, with 121 studies included in total. As expected, mortality rates were generally higher in studies with longer durations; in three large European studies, mortality rates were 30.8%, 24.4%, and 4.8% across the years 2004-2015, 2010-2018, and 2016-2020, respectively. The most frequently reported cause of death was sepsis, followed by cardiovascular complications, and disease-related mortality. GPP prevalence was 0.88-198 patients per million in the general population (9/121 studies), although the higher estimate may be inflated due to methodological approaches. Plaque psoriasis and joint disorders (affecting >40% and <20% patients in most studies, respectively) were the most frequently reported GPP-associated comorbidities (73/121 studies). In two of the largest database studies, patients with GPP experienced approximately one flare per patient-year. Mean hospitalisation duration was 8.6-30 days. This comprehensive analysis highlighted substantial between-study heterogeneity, emphasising the need for standardization of diagnostic criteria and aspects of study design (including long-term studies with sufficient patient numbers and consistent follow-up durations). Nevertheless, the epidemiological evidence indicates that GPP is a rare, potentially lethal disease with frequent comorbidities. New treatment alternatives that might improve the management of patients with GPP, to treat and prevent flares, should be evaluated urgently.