Types of Psoriasis
Psoriasis presents in several distinct clinical variants, with plaque psoriasis being the most common form affecting over 80% of patients, while other variants include inverse, erythrodermic, pustular, guttate, and nail psoriasis, each with unique clinical characteristics. 1
Major Clinical Variants of Psoriasis
1. Plaque Psoriasis (Psoriasis Vulgaris)
- Characteristics: Well-demarcated, erythematous plaques with silvery scale
- Common locations: Scalp, elbows, knees, and presacral region
- Prevalence: Most common form (>80% of cases)
- Course: May remain static or slowly enlarge; spontaneous resolution is rare 1, 2
2. Inverse (Flexural/Intertriginous) Psoriasis
- Characteristics: Erythematous plaques with minimal scaling due to moisture
- Common locations: Axillary, genital, perineal, intergluteal, inframammary areas, and antecubital fossae
- Special considerations: Requires careful steroid use due to high risk of skin atrophy 2, 1
3. Erythrodermic Psoriasis
- Characteristics: Generalized erythema covering nearly the entire body surface area with varying degrees of scaling
- Systemic symptoms: Chills, hypothermia, dehydration, fever, and malaise
- Onset: Can develop gradually from chronic plaque disease or acutely
- Severity: Considered one of the most severe forms of psoriasis 2, 1
4. Pustular Psoriasis
- Characteristics: Visible collections of neutrophils in the stratum corneum
- Subtypes:
5. Guttate Psoriasis
- Characteristics: Dew-drop-like, 1-10mm salmon-pink papules with fine scale
- Common locations: Trunk and proximal extremities
- Demographics: Common in individuals younger than 30 years
- Prevalence: Occurs in less than 2% of psoriasis patients
- Triggers: Often follows streptococcal infection 2, 1
6. Nail Psoriasis (Psoriatic Onychodystrophy)
- Prevalence: Fingernails affected in ~50% of patients, toenails in ~35%
- Characteristics: Pitting, onycholysis, subungual hyperkeratosis, and oil-drop sign
- Association: Present in up to 90% of patients with psoriatic arthritis 2, 1
Less Common Variants
7. Sebopsoriasis
- Characteristics: Combination of seborrheic dermatitis and psoriasis features
- Appearance: Greasy scales predominate, but silvery scales can be found in some areas
- Locations: Occurs at sites typical for seborrheic dermatitis 3
8. Rare Forms
- Psoriasis circinata
- Lip psoriasis
- Oral psoriasis 3
Classification by Severity
Psoriasis severity is classified based on body surface area (BSA) affected:
Important caveat: Psoriasis can be considered severe regardless of BSA when it:
- Has serious emotional consequences
- Occurs in special locations (hands, feet, scalp, face, genital area)
- Causes intractable pruritus 2, 1
Associated Conditions
Psoriatic Arthritis
Comorbidities
- Cardiometabolic diseases (dyslipidemia, metabolic syndrome, heart disease)
- Autoimmune conditions (Crohn's disease, ulcerative colitis)
- Psychological disorders 2, 4
Clinical Pearls and Pitfalls
- Location matters: Even limited BSA involvement can be considered severe when affecting special areas like face, genitals, hands, feet, or nails 1
- Diagnostic challenges: Erythrodermic psoriasis may resemble other forms of erythroderma including atopic dermatitis, contact dermatitis, seborrheic dermatitis, cutaneous T-cell lymphoma, and pityriasis rubra pilaris 2
- Treatment considerations: Avoid undertreatment of seemingly "mild" disease and overuse of high-potency topical steroids in sensitive areas 1
- Holistic approach: Always assess for associated comorbidities, especially psoriatic arthritis and cardiometabolic diseases 2, 4
Understanding the different types of psoriasis is essential for accurate diagnosis and appropriate management, as treatment approaches vary significantly based on the clinical variant, severity, and affected body areas.