Psoriasis classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Syed Hassan A. Kazmi BSc, MD [2]


Psoriasis can be classified according to clinical appearance, morphology, and localization. According to the International Psoriasis Council, psoriasis may be classified into four subtypes: plaque-type psoriasis, guttate psoriasis, generalized pustular psoriasis (GPP), and erythroderma. Several further subphenotypes have been named according to distribution (localized vs. widespread), anatomical localization (flexural or inverse, scalp, palms/soles/nail), size (large vs. small) and thickness (thick vs. thin) of plaques, onset (early vs. late), and disease activity (active vs. stable).


Classification based on clinical appearance, morphology, and localization

  • The International Psoriasis Council classifies psoriasis into four main forms, according to clinical appearance, morphology and localization:[1][2][3][4][5][6]
    • Plaque-type psoriasis
    • Guttate psoriasis
    • Generalized Pustular Psoriasis (GPP)
    • Erythroderma
Type of Psoriasis Typical Lesion Body Distribution Associated Conditions
Plaque-type psoriasis
  • Oval or irregularly shaped
  • Erythematous
  • Sharply demarcated
  • Raised plaques covered by silvery scales
  • Large plaques >3cm
  • Small plaques <3cm

Triggers include:

Guttate psoriasis
  • Multiple
  • Small
  • Drop-shaped
  • Scaly plaques
Generalized pustular psoriasis[7]
  • Generalized
Erythrodermic psoriasis (most severe)
  • >70 % of the body surface area

Classification based on sub-phenotypes

Several further sub-phenotypes have been named according to:

  • Distribution (localized vs. widespread)
  • Anatomical localization (flexural or inverse, scalp, palms/soles/nail)
  • Size (large vs. small)
  • Thickness (thick vs. thin) of plaques
  • Onset (early vs. late)
  • Disease activity (active vs. stable)

Classification based on disease severity


Psoriasis is usually graded as:

  • Mild (affecting less than 3% of the body)
  • Moderate (affecting 3-10% of the body)
  • Severe (affecting >10% of the body)

Degree of severity

The degree of severity is generally judged based on the following factors:

  • The proportion of body surface area affected
  • Disease activity (degree of plaque redness, thickness, and scaling)
  • Response to previous therapies
  • The impact of the disease on the patient's quality of life

Psoriasis Area Severity Index (PASI)

The Psoriasis Area Severity Index (PASI) is the most widely used measurement tool for psoriasis. PASI combines the assessment of the severity of lesions and the area affected into a single score ranging between 0 (no disease) to 72 (maximal disease).[8] The PASI can be very difficult to use outside of trials, which has led to attempts to simplify the index for clinical use.[9]

Other types of psoriasis

  • Napkin psoriasis
  • Seborrheic-like psoriasis
  • Pustular psoriasis

Classification of psoriatic arthritis

Psoriatic arthritis may be classified based on severity into the following types:[10]

  • Mild psoriatic arthritis
  • Moderate psoriatic arthritis
  • Severe psoriatic arthritis
Type of psoriatic arthritis Response to therapy Quality of life
Mild psoriatic arthritis NSAIDs Minimal
Moderate psoriatic arthritis Requires disease modifying anti-rheumatic drugs (DMARD) or tumor necrosis factor blockers (TNF-blockers) Daily life tasks affected including mental and physical tasks/ No response to NSAIDs
Severe psoriatic arthritis Requires disease modifying anti-rheumatic drugs (DMARD) plus tumor necrosis factor blockers (TNF-blockers) or biologic agents Unable to perform major daily tasks of living without pain or dysfunction; large impact on physical and mental functions

Psoriatic arthritis also, may be classified into different subtypes as below table:

Subtype Disease pattern[11] Percentage of patients affected Radiological features[12] Histopathological features[13][14][15]
X-ray Ultrasonography Computed tomography|CT scan MRI
Classical psoriatic arthritis ~5 %
  • Bony proliferation
  • Bone erosion
  • "Pencil-in-cup" deformity (distal head of a bone becomes pointed-like a sharpened pencil, and the neighboring surface becomes rounded due to erosion)
Destructive psoriatic arthritis (arthritis mutilans) < 5 %
Symmetric polyarthritis ~15 %
Asymmetric psoriatic arthritis
  • Does not occur in the same joints on both sides of the body
~70 %
Ankylosing spondylitis-like psoriatic arthritis
  • Stiffness of the spine or neck, but can also affect the hands and feet, in a similar fashion to symmetric arthritis
~ 5 %


  1. Boyd AS, Menter A (1989). "Erythrodermic psoriasis. Precipitating factors, course, and prognosis in 50 patients". J. Am. Acad. Dermatol. 21 (5 Pt 1): 985–91. PMID 2530253.
  2. Tauscher AE, Fleischer AB, Phelps KC, Feldman SR (2002). "Psoriasis and pregnancy". J Cutan Med Surg. 6 (6): 561–70. doi:10.1177/120347540200600608. PMID 12362257.
  3. Abel EA, DiCicco LM, Orenberg EK, Fraki JE, Farber EM (1986). "Drugs in exacerbation of psoriasis". J. Am. Acad. Dermatol. 15 (5 Pt 1): 1007–22. PMID 2878015.
  4. Skroza N, Proietti I, Pampena R, La Viola G, Bernardini N, Nicolucci F, Tolino E, Zuber S, Soccodato V, Potenza C (2013). "Correlations between psoriasis and inflammatory bowel diseases". Biomed Res Int. 2013: 983902. doi:10.1155/2013/983902. PMC 3736484. PMID 23971052.
  5. Gelfand JM, Yeung H (2012). "Metabolic syndrome in patients with psoriatic disease". J Rheumatol Suppl. 89: 24–8. doi:10.3899/jrheum.120237. PMC 3670770. PMID 22751586.
  6. Pouplard C, Brenaut E, Horreau C, Barnetche T, Misery L, Richard MA, Aractingi S, Aubin F, Cribier B, Joly P, Jullien D, Le Maître M, Ortonne JP, Paul C (2013). "Risk of cancer in psoriasis: a systematic review and meta-analysis of epidemiological studies". J Eur Acad Dermatol Venereol. 27 Suppl 3: 36–46. doi:10.1111/jdv.12165. PMID 23845151.
  7. Baker H, Ryan TJ (1968). "Generalized pustular psoriasis. A clinical and epidemiological study of 104 cases". Br. J. Dermatol. 80 (12): 771–93. PMID 4236712.
  8. "Psoriasis Update -Skin & Aging". Retrieved 2007-07-28.
  9. Louden BA, Pearce DJ, Lang W, Feldman SR (2004). "A Simplified Psoriasis Area Severity Index (SPASI) for rating psoriasis severity in clinic patients". Dermatol. Online J. 10 (2): 7. PMID 15530297.
  10. "Psoriasis: Recommendations for broadband and narrowband UVB therapy | American Academy of Dermatology".
  11. Kruithof E, Baeten D, De Rycke L, Vandooren B, Foell D, Roth J, Cañete JD, Boots AM, Veys EM, De Keyser F (2005). "Synovial histopathology of psoriatic arthritis, both oligo- and polyarticular, resembles spondyloarthropathy more than it does rheumatoid arthritis". Arthritis Res. Ther. 7 (3): R569–80. doi:10.1186/ar1698. PMC 1174942. PMID 15899044.
  12. "Psoriatic Arthritis Mutilans: Clinical and Radiographic Criteria. A Systematic Review | The Journal of Rheumatology".
  13. Kruithof E, Baeten D, De Rycke L, Vandooren B, Foell D, Roth J, Cañete JD, Boots AM, Veys EM, De Keyser F (2005). "Synovial histopathology of psoriatic arthritis, both oligo- and polyarticular, resembles spondyloarthropathy more than it does rheumatoid arthritis". Arthritis Res. Ther. 7 (3): R569–80. doi:10.1186/ar1698. PMC 1174942. PMID 15899044.
  14. Fraser A, Fearon U, Reece R, Emery P, Veale DJ (2001). "Matrix metalloproteinase 9, apoptosis, and vascular morphology in early arthritis". Arthritis Rheum. 44 (9): 2024–8. doi:10.1002/1529-0131(200109)44:9<2024::AID-ART351>3.0.CO;2-K. PMID 11592363.
  15. Fearon U, Griosios K, Fraser A, Reece R, Emery P, Jones PF, Veale DJ (2003). "Angiopoietins, growth factors, and vascular morphology in early arthritis". J. Rheumatol. 30 (2): 260–8. PMID 12563678.

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