Psoriasis — SCE Dermatology MCQ

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HardInflammatory DermatosesPsoriasisSCE Dermatology

Scalp psoriasis affects 40% of the scalp. Erythema is scored 3, induration 2 and desquamation 3, each on the PSSI 0–4 scale. What is the PSSI score?

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Correct answer: C — 24: severity sum 8 multiplied by area score 3

Explanation lettering: E = shown as A · D = shown as C · A = shown as D · C = shown as E

D is correct. PSSI adds the three scalp sign scores and multiplies that sum by the categorical area score. Erythema 3 plus induration 2 plus desquamation 3 gives 8. Involvement of 30–49% of the scalp receives area score 3, so the result is 8 × 3 = 24. A score of 8 omits extent, 16 uses a non-validated arithmetic approach, and an area score of 4 applies to 50–69%, not 40%. PSSI complements rather than replaces whole-body measures and patient-reported impact, particularly when severe scalp disease is underrepresented by total body surface area.

Reference: International Psoriasis Council PSSI assessment: https://psoriasiscouncil.org/ipc-resources/clinical-assessments/pssi/