Psoriasis

Diagnosis

• Clinical diagnosis based on well-demarcated erythematous plaques with overlying micaceous scale
• Common distribution: extensor surfaces, scalp, trunk, sacral area
• Nail findings: pitting, onycholysis, oil-drop discoloration
• Evaluate for joint symptoms suggestive of psoriatic arthritis
• Differential diagnosis includes seborrheic dermatitis, tinea corporis, cutaneous T-cell lymphoma, pityriasis rubra pilaris

Severity Assessment

• Body Surface Area (BSA) — Mild: <3%, Moderate: 3–10%, Severe: >10%
• Investigator Global Assessment (IGA)
• PASI (Psoriasis Area and Severity Index)
• DLQI for quality-of-life impact
• Special site involvement (scalp, nails, palms/soles, genital) may warrant systemic therapy regardless of BSA

Treatment Stratification

• Mild: Topical corticosteroids, vitamin D analogues, combination topical therapies, non-steroidal topicals
• Moderate: Phototherapy or systemic therapy based on distribution and patient factors and quality-of-life impact
• Moderate-to-Severe: Biologic therapy (IL-17, IL-23, IL-12/23 inhibitors, TNF inhibitors), TYK2 inhibitors,oral small molecules