Psoriasis Vulgaris: A Comprehensive Clinical Review

Introduction

Psoriasis vulgaris, the most prevalent form of psoriasis, is a chronic, immune-mediated inflammatory skin disorder characterized by well-demarcated erythematous plaques with silvery scales. It affects approximately 2–3% of the global population and has profound impacts on quality of life, psychological well-being, and systemic health. Psoriasis often follows a relapsing-remitting course, with flares influenced by genetic predisposition, environmental triggers, and immune dysregulation.

Epidemiology and Risk Factors

• Prevalence & Demographics: Affects 2–3% of adults worldwide; bimodal onset peaks at 20–30 years and 50–60 years. No strong gender predilection, though severity may differ by sex and ethnicity.
• Genetic Susceptibility: Over 60 psoriasis susceptibility loci (PSORS1–PSORS9) have been identified. HLA-C*06:02 is strongly linked to early-onset disease and guttate variants.
• Environmental and Lifestyle Triggers:
• Infections: Streptococcal pharyngitis can precipitate guttate psoriasis.
• Stress: Psychological stress and depression correlate with flares.
• Medications: Beta-blockers, lithium, antimalarials, NSAIDs.
• Smoking & Alcohol: Increase risk and severity.
• Trauma: Koebner phenomenon (isomorphic response) occurs in up to 25% of patients after skin injury.

Pathophysiology

1. Immune Activation: Dendritic cells release IL-12 and IL-23, driving Th1 and Th17 differentiation.
2. Cytokine Cascade: Th17 cells produce IL-17A, IL-17F, IL-22, and TNF-α, promoting keratinocyte hyperproliferation and neutrophil recruitment.
3. Keratinocyte Dysfunction: Abnormal differentiation leads to parakeratosis and incomplete maturation, producing the characteristic silvery scale.

Clinical Presentation

Typical Features

• Plaques: Sharply defined, erythematous, and scaly; commonly on extensor surfaces (elbows, knees), scalp, lumbosacral area, and intergluteal cleft.
• Scale Characteristics: Silvery-white, thick scales — the Auspitz sign (pinpoint bleeding upon scale removal) and the candle-dripping phenomenon (wax drop sign) are diagnostic hallmarks.
• Distribution: Symmetrical; the scalp often shows thick, adherent scale extending beyond the hairline. Nail involvement occurs in up to 50% of cases (pitting, onycholysis, subungual hyperkeratosis).

Special Variants and Manifestations

• Guttate Psoriasis: Small, droplet-like papules often triggered by streptococcal infection.
• Inverse (Intertriginous) Psoriasis: Smooth, erythematous plaques in skin folds lacking typical scale due to moisture and friction.
• Pustular Psoriasis: Localized (e.g., palmoplantar) or generalized sterile pustules with systemic symptoms.
• Erythrodermic Psoriasis: Diffuse erythema and scaling covering >80% body surface area; risk of hemodynamic instability and thermoregulatory dysfunction.
• Arthropathic Psoriasis (Psoriatic Arthritis): Occurs in up to 30% of patients; may precede or follow skin lesions. Patterns include asymmetric oligoarthritis, symmetric polyarthritis, distal interphalangeal predominant, spondylitis, and arthritis mutilans.

Diagnosis and Severity Assessment

• Clinical Diagnosis: Based on morphology, distribution, and family history; skin biopsy reserved for atypical presentations.
• Severity Scoring:
• PASI (Psoriasis Area and Severity Index): Gold standard; incorporates lesion severity (erythema, induration, scaling) and body surface area.
• BSA (Body Surface Area) and PGA (Physician Global Assessment) for rapid clinic use.
• DLQI (Dermatology Life Quality Index): Patient-reported outcome assessing QoL impact.

Differential Diagnosis

• Seborrheic dermatitis, eczema, tinea corporis, lichen planus, and pityriasis rosea. Nail psoriasis vs onychomycosis. Koebner phenomenon must be distinguished from pathergy in other disorders.

Comorbidities and Systemic Impact

• Cardiometabolic: Increased risk of obesity, metabolic syndrome, cardiovascular disease; severity correlates with systemic inflammation.
• Psychosocial: Depression, anxiety, social stigma; higher rates of suicidal ideation in severe disease.
• Other Autoimmune: Inflammatory bowel disease, uveitis, and autoimmune thyroid disease.

Management

Topical Therapies (Mild to Moderate Disease)

• Corticosteroids: Mid- to high-potency applied 1–2 times daily; taper with improvement to minimize side effects.
• Vitamin D Analogues: Calcipotriol or calcitriol to normalize keratinocyte proliferation; use combination products to enhance efficacy and reduce steroid exposure.
• Topical Retinoids: Tazarotene for plaque psoriasis; caution in pregnancy and mucosal areas.
• Calcineurin Inhibitors: Tacrolimus or pimecrolimus for inverse psoriasis and sensitive areas.

Phototherapy

• Narrow-band UVB (NB-UVB): Standard for moderate disease; thrice-weekly sessions.
• PUVA (Psoralen + UVA): Effective but limited by long-term risks; reserved for refractory cases.
• Excimer Laser (308 nm): Targeted therapy for localized plaques.

Systemic Therapies (Moderate to Severe Disease)

• Traditional Systemics:
• Methotrexate: Weekly dosing (7.5–25 mg) with folate supplementation; monitor liver and hematologic parameters.
• Cyclosporine: Rapid onset (3–6 mg/kg/day) for short-term control; nephrotoxicity limits long-term use.
• Acitretin: Oral retinoid (25–50 mg/day) effective in pustular variants; teratogenic with prolonged washout period.
• Biologic Agents: Targeted immunomodulators revolutionizing psoriasis care; selection guided by comorbidities and safety profile:
• TNF-α Inhibitors: Etanercept, infliximab, adalimumab.
• IL-12/23 Inhibitor: Ustekinumab.
• IL-17 Inhibitors: Secukinumab, ixekizumab, brodalumab.
• IL-23 Inhibitors: Guselkumab, tildrakizumab, risankizumab.
• Small Molecules: Apremilast (PDE4 inhibitor) and emerging JAK inhibitors for patients preferring non-injectable options.

Psoriatic Arthritis Management

• DMARDs: Methotrexate, leflunomide for peripheral arthritis.
• Biologics: Effective for both skin and joint manifestations—TNF inhibitors, IL-17/23 inhibitors.

Monitoring and Follow-Up

• Assessment Frequency: Office visits every 3–6 months for stable disease; more frequent for treatment initiation or changes.
• Laboratory Monitoring: CBC, LFTs, renal function for systemic therapies; tuberculosis screening before biologics; periodic lipid profiles for retinoids.
• Vaccinations: Ensure up-to-date immunizations, including pneumococcal and influenza vaccines, especially before initiating biologics.

Patient Education and Adherence

• Educate on chronic nature, realistic expectations, and importance of adherence to therapy.
• Train on proper topical application techniques and sun protection during phototherapy.
• Provide support for lifestyle modifications—smoking cessation, weight management, stress reduction.

Conclusion

Psoriasis vulgaris is a multifaceted, systemic disease necessitating a personalized, multidisciplinary management approach. Advances in targeted immunotherapies have dramatically improved outcomes, yet vigilant monitoring, patient education, and holistic care are paramount to optimize long-term disease control and quality of life.