Psoriasis Vulgaris

Skin Lesion: Well-demarcated, erythematous, salmon-pink plaques covered with silvery-white scales. Auspitz sign (pinpoint bleeding upon scale removal) is often positive.

Classic Distribution:

Favors EXTENSOR surfaces such as elbows, knees, scalp, and the sacral area. It may also involve the nails (pitting, onycholysis).

Pityriasis Rosea

• The Clue: Self-limiting eruption starting with a single Herald Patch followed by a "Christmas Tree" distribution.
• Vs Psoriasis: Scales are "collarette" (attached at the periphery). Lesions are typically oval and much thinner than psoriatic plaques.

Discoid (Nummular) Eczema

• The Clue: Intensely itchy, coin-shaped (nummular) lesions.
• Vs Psoriasis: Lacks the thick silvery-white scale. Distribution is usually random on the limbs rather than specific to extensor surfaces.

• BSA > 10%: Involvement of more than 10% total body surface area (Note: 1 patient palm ≈ 1% BSA).
• Critical Areas: Involvement of the face, genitalia, palms, or soles.
• Severe Forms: Suspected Erythrodermic or Pustular psoriasis (Urgent).
• Treatment Failure: Poor response to appropriate potent topical therapy.
• Systemic Symptoms: Suspicion of Psoriatic Arthritis (joint pain/stiffness).

Topical Steroid
• Very Potent: Clobetasol BD.
• Potent: Betamethasone BD.

Symptomatic
• Emollients: Liberal use of White Soft Paraffin.
• Coal Tar: Topical preparations for plaque de-scaling.

Antihistamine
• Loratadine 10mg OD
• Cetirizine 10mg OD
• Piriton 4mg ON/TDS

⚠️ Safety Pearl: Generally limit high-potency TCS to <2 weeks duration. Avoid systemic steroids as withdrawal may trigger life-threatening Pustular Psoriasis.