Krueger et al classified the severity of psoriasis based on its impact on the patient. The authors are from multiple hospitals from the United States.


Patient selection: psoriasis



(1) impact on quality of life (QOL)

(2) need for treatment

(3) hazards of therapy

(4) percent of body surface area (BSA) affected

(5) other factors


Mild Psoriasis

Moderate Psoriasis

Severe Psoriasis

impact on QOL

little or none



need for treatment

little or none



hazards of therapy

little or none

little but may be bothersome or expensive to use

may be serious, often does not respond to therapy with minimal side effects

percent BSA

< 5%

2 to 20%

> 10%


Other factors that may make psoriasis severe:

(1) patient’s negative attitude about the disease (depression, anxiety, social withdrawal, etc)

(2) location of lesions (face, hands, fingernails, scalp, feet, genitals)

(3) arthralgias or arthritis

(4) symptoms


In mild disease the patient can minimize the impact of the disease so has some sense of control over the condition.


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