What is Plaque Psoriasis
Plaque psoriasis is a chronic, immune-mediated inflammatory skin disease characterized by well-demarcated, raised, erythematous (red) plaques covered with silvery-white scales that are often intensely itchy or painful 1, 2.
Core Clinical Features
Plaque psoriasis (also called psoriasis vulgaris) presents with:
- Scaly, erythematous patches, papules, and plaques that are typically pruritic 1
- Silvery-white, dry scale overlying circular, well-circumscribed red plaques 2, 3
- Symmetric distribution most commonly on the scalp, elbows, knees, lumbosacral area, and body folds 3
This is the most common form of psoriasis, affecting approximately 2% of the U.S. population 1, 2.
Pathophysiology
Plaque psoriasis is fundamentally a T-cell-mediated autoimmune disease with a strong genetic component 2. The disease involves:
- Dysregulated crosstalk between immune cells (particularly T cells) and skin-resident cells like keratinocytes 4
- Chronic inflammation driven by cytokine pathways, especially the IL-23/Th17 axis 4
- Genetic predisposition - approximately 30% of patients have a first-degree relative with the disease 2
- Environmental triggers that can precipitate or worsen disease (certain medications, infections, sun exposure) 2, 5
Disease Behavior and Impact
Plaque psoriasis is a lifelong chronic disease that waxes and wanes, with few spontaneous remissions 1. Key characteristics include:
- Disfiguring lesions that cause significant quality of life impairment 1
- Tendency to recur in the same locations after treatment discontinuation, due to persistent immune memory cells in the skin (termed "molecular scarring") 6
- Disease activity fluctuates with treatment initiation and cessation 1
Associated Conditions
This is a systemic inflammatory disorder, not just a skin disease 1. Patients have increased risk of:
- Psoriatic arthritis (inflammatory joint disease affecting up to 30% of psoriasis patients) 1
- Cardiovascular disease and metabolic syndrome components 1, 7
- Inflammatory bowel disease 1
- Psychological comorbidities 7
- Nail involvement (psoriatic onychodystrophy) occurs in approximately 50% of patients 1
Diagnostic Approach
Diagnosis is primarily clinical, based on characteristic physical findings and history 8. The distinctive appearance of well-demarcated plaques with silvery scale in typical locations usually makes the diagnosis straightforward, though skin biopsy may occasionally be needed when presentation is atypical 2, 8.