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PASI (Psoriasis Area and Severity Index)

Also called PASI, psoriasis severity score

Plaque psoriasis extent and severity across four body regions (0–72).

Head and neck: area involved
Head and neck: erythema
Head and neck: induration (thickness)
Head and neck: desquamation (scaling)
Upper limbs: area involved
Upper limbs: erythema
Upper limbs: induration (thickness)
Upper limbs: desquamation (scaling)
Trunk: area involved
Trunk: erythema
Trunk: induration (thickness)
Trunk: desquamation (scaling)
Lower limbs: area involved
Lower limbs: erythema
Lower limbs: induration (thickness)
Lower limbs: desquamation (scaling)

Fill 16 more fields to see the result.

Formula and scoring

For each region: (erythema + induration + desquamation, each 0–4) × area score (0–6) × weight. Weights: head 0.1, upper limbs 0.2, trunk 0.3, lower limbs 0.4. PASI = sum of the four regions (max 72).

Exam and ward pearls

  • Response endpoints: PASI 75 / 90 / 100 = 75%, 90% or 100% fall from baseline; ΔPASI <50% means change therapy (European consensus).
  • Rule of tens (Finlay): BSA >10% or PASI >10 or DLQI >10 = severe psoriasis.

When not to rely on it

  • PASI measures signs only; pair it with DLQI, which the European consensus uses alongside PASI and BSA.

Source

  1. Fredriksson T, Pettersson U. Severe psoriasis — oral therapy with a new retinoid. Dermatologica. 1978;157(4):238-44. doi:10.1159/000250839 · PMID 357213
  2. Oakley A. PASI score. DermNet (scoring method: region weights, area score bands, 0–4 severity). Link
  3. Mrowietz U, Kragballe K, Reich K, et al. Definition of treatment goals for moderate to severe psoriasis: a European consensus. Arch Dermatol Res. 2011;303(1):1-10. doi:10.1007/s00403-010-1080-1 · PMID 20857129
  4. Finlay AY. Current severe psoriasis and the rule of tens. Br J Dermatol. 2005;152(5):861-7. doi:10.1111/j.1365-2133.2005.06502.x · PMID 15888138

Formula and cut-offs checked against these sources on 8 Nov 2026. Educational tool for clinicians; it does not replace clinical judgement.

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