Scalp Psoriasis

Introduction & Pathogenesis - Scalp Under Siege

• Definition: Common chronic inflammatory dermatosis; well-demarcated, erythematous plaques with thick, silvery-white scales on the scalp. Often pruritic.
• Onset: Typically bimodal: 20-30 years and 50-60 years.
• Pathogenesis: Immune-mediated, T-cell driven inflammation.
  • Key cytokines: TNF-α, IL-23/IL-17 axis.
  • Results in keratinocyte hyperproliferation & abnormal differentiation.
• Genetics: Strong predisposition; HLA-Cw6 is a key associated allele.

⭐ Scalp is the most common initial site for psoriasis in ~50% of patients and affects up to 80% of psoriasis patients at some point.

Clinical Features - Itchy Crown Clues

• Appearance: Well-demarcated, erythematous plaques with thick, adherent, silvery-white scales.
  • May be diffuse or patchy, sometimes forming a "Psoriatic cap" (thick, crusted lesions covering the entire scalp).
• Common Sites: 📌 Hairline, Occiput, Vertex, Retroauricular areas. (Mnemonic: Hairy Old Vampire's Red scalp)
• Symptoms:
  • Pruritus: Often intense and a primary complaint.
  • Bleeding: Occurs with scratching or scale removal.
• Specific Signs:
  • Auspitz sign: Pinpoint bleeding points when scales are scraped off.
  • Koebner phenomenon: Development of lesions at sites of trauma.

⭐ Auspitz sign (pinpoint bleeding on removal of scales) is characteristic but not specific to psoriasis.

Differential Diagnosis - Scalp Look-Alikes

Key conditions mimicking scalp psoriasis include:

Other important differentials:

• Lichen Planopilaris: Scarring alopecia, perifollicular erythema/scaling.
• Atopic Dermatitis (Scalp Eczema): Intense pruritus, history of atopy, lichenification.

⭐ Histopathology of psoriasis: Parakeratosis, Munro's microabscesses (neutrophils in stratum corneum), acanthosis with elongated rete ridges (club-shaped).

Management Strategies - Taming the Flakes

• Goals: Control inflammation, scaling, itch; improve Quality of Life (QoL).

• Topical (1st Line): Crucial for most.

  • Corticosteroids: Potency selection vital (e.g., clobetasol propionate 0.05%). Scalp-friendly: lotions, solutions, foams, shampoos.
  • Vitamin D analogues: Calcipotriol, calcitriol. Often combined with steroids.
  • Keratolytics: Salicylic acid (removes scales).
  • Coal tar: Shampoos, solutions (anti-proliferative).
  • Combination products: e.g., steroid + Vit D analogue.

• Systemic Therapy (Severe/Refractory):

  • Indications: Extensive, unresponsive disease; ↓QoL.
  • Options: Methotrexate, Cyclosporine, Apremilast.
  • Biologics: Anti-TNF, Anti-IL17, Anti-IL23 agents (class names).

• Phototherapy: Narrowband UVB (NB-UVB) for widespread scalp psoriasis.

⭐ For topical therapy, foams and solutions are generally preferred for hairy areas like the scalp due to ease of application and cosmetic acceptability.

High‑Yield Points - ⚡ Biggest Takeaways

• Chronic inflammatory condition presenting as well-demarcated erythematous plaques with silvery-white scales, often beyond hairline (psoriatic corona).
• Auspitz sign (pinpoint bleeding on scale removal) is highly suggestive.
• Koebner phenomenon (new lesions at trauma sites) can occur.
• Frequently associated with psoriatic nail changes (pitting, onycholysis).
• Differentiate from seborrheic dermatitis (greasy, yellowish scales, less demarcation).
• First-line therapy: Topical corticosteroids and vitamin D analogues.
• Pityriasis amiantacea is a severe variant with asbestos-like scales an_d adherent hair m_atting_._