Generalised pustular psoriasis (GPP) is a rare, potentially life-threatening autoinflammatory neutrophilic skin disease characterised by episodes of widespread eruption of sterile, macroscopically visible pustules, which can occur with or without plaque psoriasis. Acute GPP flares may be accompanied by systemic symptoms such as fever, malaise, and laboratory abnormalities including elevated C-reactive protein, leucocytosis, and neutrophilia. Without appropriate treatment, severe flares can lead to significant morbidity and mortality.

The Generalised Pustular Psoriasis Physician Global Assessment (GPPGA) is a physician-reported clinical instrument developed to evaluate overall GPP disease severity. It was created alongside the GPPASI by adapting the Physician Global Assessment (PGA) framework commonly used in plaque psoriasis, with modifications specific to the pustular phenotype of GPP. The GPPGA was first used as an endpoint in the Effisayil 1 trial (Bachelez et al., 2021), the first randomised, double-blind, placebo-controlled study in patients presenting with an acute GPP flare.

The GPPGA evaluates three clinical characteristics of GPP lesions: erythema, pustulation, and scaling (desquamation). Each component is graded separately on a 5-point scale ranging from 0 (clear) to 4 (severe). In the global assessment mode, the GPPGA total score is the arithmetic mean of the three component scores, yielding a continuous value from 0 to 4. The GPPGA can also be assessed regionally, where each body region (head and neck, upper extremities, trunk, lower extremities) is scored independently for all three components; the regional composite for each region is (E + P + D) / 3, and the GPPGA total score is the mean of the four regional composites. Both approaches yield a score in the 0 to 4 range. The pustulation subscore (the pustulation component alone, or its regional mean) is reported separately, as it reflects the defining clinical feature of GPP and was used as the primary efficacy endpoint in the Effisayil 1 trial.

Psychometric validation by Burden et al. (2023) demonstrated that the GPPGA has good test-retest reliability and correlates with the GPPASI, supporting its use as a valid and responsive measure of GPP severity. In the Effisayil 1 trial, spesolimab demonstrated superiority over placebo for both the primary endpoint (GPPGA pustulation subscore of 0 at Week 1) and the key secondary endpoint (GPPGA total score of 0 or 1 at Week 1). The achievement of a GPPGA score of 0 or 1 (clear or almost clear) is considered a clinically meaningful treatment response.