Psoriasis classification

Psoriasis Microchapters
Home
Patient Information
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Psoriasis from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
History and Symptoms
Physical Examination
Laboratory Findings
X-ray
Ultrasound
CT scan
MRI
Other Imaging Studies
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Primary Prevention
Secondary Prevention
Cost-Effectiveness of Therapy
Future or Investigational Therapies
Case Studies
Case #1
Psoriasis classification On the Web
Most recent articles
Most cited articles
Review articles
CME Programs
Powerpoint slides
Images
American Roentgen Ray Society Images of Psoriasis classification All Images X-rays Echo & Ultrasound CT Images MRI
Ongoing Trials at Clinical Trials.gov
US National Guidelines Clearinghouse
NICE Guidance
FDA on Psoriasis classification
CDC on Psoriasis classification
Psoriasis classification in the news
Blogs on Psoriasis classification
Directions to Hospitals Treating Psoriasis
Risk calculators and risk factors for Psoriasis classification

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

Overview

Psoriasis can be classified according to clinical appearance, morphology and localization. According to International Psoriasis Council, psoriasis may be classified into 4 subtypes: plaque-type psoriasis, guttate psoriasis, generalized pustular psoriasis (GPP), erythroderma. Several further subphenotypes have been named according to distribution (localized vs. widespread), anatomical localization (flexural - also called 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

Psoriasis can be classified according to clinical appearance, morphology and localization.

• The International Psoriasis Council, classifies psoriasis into four main forms:
  • Plaque-type psoriasis
  • Guttate psoriasis
  • Generalized Pustular Psoriasis (GPP)
  • Erythroderma

Type of Psoriasis	Typical lesion	Body Distribution	Associated conditions
Plaque-type psoriasis (most common)	Oval or irregularly shaped, red, sharply demarcated, raised plaques covered by silvery scales.	Large plaques > 3cm Small plaques < 3cm Extensor surface of elbows and knees Scalp Lower back
Guttate psoriasis	Multiple, small, drop-shaped, scaly plaques	trunk Upper extremities Thighs	2–4 weeks after a bacterial infection of the upper ways, notably streptococcal pharyngitis in children and adolescents
Generalized pustular psoriasis	Four sub-types namely: Zumbusch (erythema, sheeted pustulation and scarlatiniform peeling) Annular (gyrate and annular pustular lesions) Localized (restricted areas of pustular psoriasis in and around ordinary psoriatic plaques) Exanthematic (single short-lived episode following infection or drug exposure) Episodic, widespread skin and systemic inflammation. Sheeted, pinhead-sized, sterile, sub-corneal pustules		High fever fatigue leukocytosis Triggers include: Pregnancy Infection Exposure to or withdrawal from drugs
Erythrodermic psoriasis (most severe)	Diffuse erythema	>70 % of the body surface area	Hypothermia Extremity edema Myalgias Fatigue High grade fever

Several further subphenotypes have been named according to distribution (localized vs. widespread), anatomical localization (flexural- also called 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).

Other types of psoriasis

• Flexural psoriasis (inverse psoriasis) appears as smooth inflamed patches of skin. It occurs in skin folds, particularly around the genitals (between the thigh and groin), axillae, under an overweight stomach (pannus), and under the breasts (inframammary fold). It is aggravated by friction and sweat, and is vulnerable to fungal infections.
• Nail psoriasis produces a variety of changes in the appearance of finger and toe nails. These changes include discolouring under the nail plate, pitting of the nails, lines going across the nails, thickening of the skin under the nail, and the loosening (onycholysis) and crumbling of the nail.
• Drug-induced psoriasis
• Napkin psoriasis
• Seborrheic-like psoriasis
• Pustular psoriasis

• 
  Photograph of an arm covered with plaque psoriasis.
• 
  Psoriasis nail pitting

Severity

Pie chart showing the distribution of severity among people with psoriasis.

Psoriasis is usually graded as:

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

Degree of severity

The degree of severity is generally 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 person.

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 in the range 0 (no disease) to 72 (maximal disease). The PASI can be too unwieldy to use outside of trials, which has led to attempts to simplify the index for clinical use.