Clinical Presentation & Dermoscopy

Chronic plaque psoriasis (psoriasis vulgaris) presents with sharply demarcated, erythematous plaques covered by silvery-white micaceous scale on extensor surfaces (elbows, knees), lumbosacral back, scalp, and umbilicus.

• Auspitz Sign: Pinpoint bleeding upon removal of adherent scale due to thinned suprapapillary plates and dilated tortuous dermal capillaries.
• Koebner Phenomenon: Development of isomorphic psoriatic lesions at sites of cutaneous trauma within 10–14 days.
• Dermoscopy (Inflammoscopy): Regularly distributed, uniform dotted (glomerular) vessels over a light-red background with diffuse white scales.

Histopathology

• Regular (test-tube) psoriasiform epidermal hyperplasia with elongated rete ridges.
• Thinning of suprapapillary epidermal plates.
• Confluent parakeratosis with Munro microabscesses (neutrophils in stratum corneum) and spongiform pustules of Kogoj (neutrophils in spinous layer).

Severity Assessment & Therapeutic Ladder

1. Mild (<3–5% BSA, PASI <10): Superpotent topical corticosteroid (Clobetasol 0.05%) + Calcipotriol foam/ointment; Roflumilast 0.3% or Tapinarof 1% cream for intertriginous/facial sites.
2. Moderate-to-Severe (PASI ≥10, BSA ≥10%, or DLQI >10):
   • Phototherapy: Narrowband UVB (311 nm) 3×/week.
   • Conventional Systemics: Methotrexate (15–25 mg/week + Folic acid 5 mg), Ciclosporin (2.5–5 mg/kg/day up to 16 weeks), Acitretin (0.25–0.5 mg/kg/day; strictly contraindicated for 3 years prior to conception).
   • Targeted Biologics & Oral Small Molecules:
     • IL-23p19 Inhibitors (Risankizumab, Guselkumab, Tildrakizumab): Highest long-term PASI-90/100 durability; safe in IBD.
     • IL-17 Inhibitors (Secukinumab, Ixekizumab, Bimekizumab): Fastest onset of skin clearance; screen for candidiasis and avoid in IBD.
     • TYK2 Inhibitor (Deucravacitinib 6 mg OD): Allosteric TYK2 inhibitor without JAK1–3 laboratory monitoring burden.