Generalised Pustular Psoriasis Area and Severity Index

Physician-Reported Clinical Assessment

A validated clinical tool for quantifying generalised pustular psoriasis severity, adapted from the PASI with pustulation replacing induration. Evaluates four body regions across three severity characteristics with standard and high-discrimination scoring modes.

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April 27, 2026
12:06 a.m.

Generalised Pustular Psoriasis Area and Severity Index

Standard GPPASI

0.0

/ 72

Clear / almost clear

Estimated BSA: ~0.0%

Region Breakdown

Region	Weight	E	P	D	Area	Score
Head and Neck	0.1	0	0	0	0	0.0
Upper Extremities	0.2	0	0	0	0	0.0
Trunk	0.3	0	0	0	0	0.0
Lower Extremities	0.4	0	0	0	0	0.0

Calculation

Region score = W × (E + P + D) × A

Head: 0.1 × (0 + 0 + 0) × 0 = 0.0

Upper: 0.2 × (0 + 0 + 0) × 0 = 0.0

Trunk: 0.3 × (0 + 0 + 0) × 0 = 0.0

Lower: 0.4 × (0 + 0 + 0) × 0 = 0.0

Total: 0.0

For clinical use only. Generated by CMSD Clinical Tools.

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Scoring Mode

Standard GPPASI scores area involvement using broad brackets. GPPASI-HD provides finer 1% granularity below 10% involvement. Learn more

Palm method for area estimation

1 patient palm (including fingers) ≈ 1% of total BSA. Learn more

Head and Neck

Weight: 10% of total BSA

Region score

0.0

Area of Involvement

Erythema

Pustules

Desquamation

Upper Extremities

Weight: 20% of total BSA

Region score

0.0

Area of Involvement

Erythema

Pustules

Desquamation

Trunk

Weight: 30% of total BSA

Region score

0.0

Area of Involvement

Erythema

Pustules

Desquamation

Lower Extremities

Weight: 40% of total BSA

Region score

0.0

Area of Involvement

Erythema

Pustules

Desquamation

0.0/ 72Clear / almost clear

=0.0+0.0+0.0+0.0

Developed in partnership withDermi

About the GPPASI

Severity Bands

Score Range	Classification	Interpretation
0 – 3	Clear / almost clear	Minimal or no GPP disease activity
3.1 – 7	Mild	Mild GPP
7.1 – 10	Moderate	Moderate GPP
10.1 – 20	Severe	Severe GPP
20.1 – 72	Very severe	Very severe GPP

Clinical Background

Generalised pustular psoriasis (GPP) is a rare, severe form of neutrophilic skin disease characterised by widespread eruption of sterile pustules on erythematous skin. Unlike plaque psoriasis, GPP can present with systemic symptoms including fever, malaise, and laboratory abnormalities. The condition may occur independently or in patients with a history of plaque psoriasis, and flares can be life-threatening without prompt treatment.

The GPPASI was developed by adapting the Psoriasis Area and Severity Index (PASI), first published by Fredriksson and Pettersson in 1978. The key modification replaces the induration (thickness) component of PASI with a pustulation score, reflecting the defining clinical feature of GPP. Erythema and desquamation scoring remain unchanged. The GPPASI evaluates four body regions (head, upper extremities, trunk, lower extremities) with the same area weighting as PASI: head = 0.1, upper extremities = 0.2, trunk = 0.3, lower extremities = 0.4.

Each body region is assessed for three severity characteristics (erythema, pustules, desquamation), each graded 0 to 4, and for percentage of body surface area involvement (scored 0 to 6). The region score is calculated as weight multiplied by the sum of the three severity grades multiplied by the area score. The total GPPASI is the sum of all four regional scores, ranging from 0 to 72. Higher scores indicate more severe disease.

Psychometric validation by Burden et al. (2023) demonstrated good test-retest reliability for the GPPASI (intraclass correlation coefficient = 0.95). A clinically meaningful improvement was defined as a GPPASI reduction of 12.0 points or greater. The GPPASI has been used as a secondary efficacy endpoint in clinical trials for GPP, including the pivotal Effisayil 1 spesolimab trial (Bachelez et al., 2021). Severity band thresholds have not been formally established for GPPASI; the classifications used here are extrapolated from PASI equivalence given the identical scoring methodology and score range.

References

Fredriksson T, Pettersson U. Severe psoriasis - oral therapy with a new retinoid. Dermatologica. 1978;157(4):238-244. doi:10.1159/000250839
Bachelez H, Choon SE, Marrakchi S, Burden AD, Tsai TF, Morita A, Navarini AA, Zheng M, Xu J, Turki H, Anadkat MJ, Rajeswari S, Hua H, Vulcu SD, Hall D, Tetzlaff K, Thoma C, Lebwohl MG. Trial of spesolimab for generalized pustular psoriasis. N Engl J Med. 2021;385(26):2431-2440. doi:10.1056/NEJMoa2111563
Choon SE, Lebwohl MG, Marrakchi S, Burden AD, Tsai TF, Morita A, Navarini AA, Zheng M, Xu J, Turki H, Rajeswari S, Deng H, Tetzlaff K, Thoma C, Bachelez H. Study protocol of the global Effisayil 1 Phase II, multicentre, randomised, double-blind, placebo-controlled trial of spesolimab in patients with generalized pustular psoriasis presenting with an acute flare. BMJ Open. 2021;11(3):e043666. doi:10.1136/bmjopen-2020-043666
Burden AD, Bissonnette R, Lebwohl MG, Gloede T, Anatchkova M, Budhiarso I, Hu N, Thoma C, Skalicky AM, Bachelez H. Psychometric validation of the generalized pustular psoriasis physician global assessment (GPPGA) and generalized pustular psoriasis area and severity index (GPPASI). J Eur Acad Dermatol Venereol. 2023;37(7):1327-1335. doi:10.1111/jdv.18999

Frequently Asked Questions about the GPPASI

The Generalised Pustular Psoriasis Area and Severity Index (GPPASI) is a physician-reported instrument for quantifying the severity of generalised pustular psoriasis (GPP). It evaluates four body regions (head, upper extremities, trunk, lower extremities) across three severity characteristics: erythema, pustules, and desquamation. Scores range from 0 to 72, with higher scores indicating more severe disease.

For each of the four body regions, the area of involvement is scored from 0 to 6 and multiplied by the sum of three severity scores (erythema, pustules, and desquamation, each scored 0 to 4). Each region is then weighted by its proportion of total body surface area: head = 0.1, upper extremities = 0.2, trunk = 0.3, lower extremities = 0.4. The total GPPASI is the sum of all four weighted regional scores.

The GPPASI was adapted from the PASI by replacing the induration (thickness) component with a pustulation score. This reflects the defining clinical feature of generalised pustular psoriasis, where sterile pustules rather than raised plaques are the primary finding. Both instruments share the same body regions, area scoring, weighting system, and score range (0 to 72).

Generalised pustular psoriasis is a rare, severe form of neutrophilic skin disease characterised by widespread eruption of sterile pustules on erythematous skin. GPP can present with systemic symptoms including fever, malaise, and laboratory abnormalities. Flares can be life-threatening and require prompt medical treatment. GPP may occur independently or in patients with a history of plaque psoriasis.

The theoretical maximum GPPASI score is 72, representing complete involvement of all four body regions with the most severe lesion characteristics (erythema, pustules, and desquamation each scored at 4 in every region). In clinical trials, a reduction of 12.0 points or greater from baseline has been defined as a clinically meaningful improvement.

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