Psoriasis

Related Subjects: |Nikolsky's sign |Koebner phenomenon |Psoriatic Arthritis |Psoriasis |Eczema/Dermatitis |Anatomy of Skin | Topical Steroids

🩺 Psoriasis = chronic, relapsing-remitting inflammatory skin disease. Characterised by well-demarcated erythematous plaques with silvery scales. Onset often 10–30 yrs. Significant morbidity due to disfigurement, itching, psychological impact, and risk of psoriatic arthritis.

📖 About

• Definition: Autoimmune condition with accelerated epidermal turnover → thick scaly plaques.
• Pathophysiology: Keratinocyte maturation shortened from 21–28 days to ~7 days.
• Associated: Psoriatic arthropathy (dactylitis, sacroiliitis, arthritis).

🧪 Aetiology

• 👫 Affects males & females equally.
• 🧬 Genetic predisposition + family history.
• 🛡️ Immunological: T-cell mediated, chronic inflammation.
• 🧱 Pathological: keratinocyte proliferation, angiogenesis.
• ⚡ Triggers: stress, infections, trauma (Koebner phenomenon), smoking, alcohol, certain drugs (β-blockers, lithium, NSAIDs, antimalarials).

📌 Types of Psoriasis

• 🟥 Chronic plaque psoriasis: Most common. Extensor plaques with silvery scale.
• 💧 Guttate psoriasis: “Raindrop” lesions post-streptococcal infection in young patients.
• 🟡 Seborrhoeic psoriasis: Affects nasolabial folds, scalp, retroauricular areas.
• 🔄 Flexural (inverse): Shiny red lesions in body folds (axillae, inframammary).
• 🔥 Erythrodermic psoriasis: Rare, life-threatening, widespread erythema/scaling → admit.
• 👣 Palmar-plantar pustulosis: Sterile pustules on palms/soles.

⚡ Clinical Features

• Red plaques, silvery scales (classically elbows, knees, scalp, lumbosacral area).
• Koebner phenomenon: new lesions at trauma sites.
• Scalp: thick adherent plaques.
• Nails: pitting, onycholysis, “oil drop” sign.
• Pustules (localized/generalized).
• Erythrodermic psoriasis → urgent review.

🔀 Differential Diagnosis

• Pityriasis rosea vs guttate psoriasis.
• Scalp psoriasis vs seborrhoeic dermatitis (dandruff).
• Chronic eczema vs flexural psoriasis.

🔎 Investigations

• Usually clinical diagnosis.
• Skin biopsy if atypical.
• Screen for comorbidities: metabolic syndrome, diabetes, cardiovascular disease.

💊 Management

• 👩‍⚕️ Referral: To dermatology if diagnosis uncertain, extensive disease, occupational impact, face/palm/genital involvement, poor response to 2–3 months of topicals, severe/recalcitrant cases, or suspected psoriatic arthritis → rheumatology.

🧴 Topical Therapies

• 💧 Emollients: 3–4× daily. Reduce scaling, itching.
• 🧪 Vitamin D analogues: Calcipotriol, tacalcitol, calcitriol. Often first-line with/without steroids.
• 💊 Topical corticosteroids: Useful for plaques, scalp, flexures (short-term).
• 🟤 Coal tar: Anti-inflammatory, odorous but effective. Can combine with salicylic acid for scaling.
• 🟣 Dithranol: For large plaques. Effective but irritant, stains skin.
• 🧴 Topical retinoids (tazarotene): Mild–moderate plaque psoriasis.
• 🧠 Psychological support: Important given stigma and mental health impact.
• 📅 Follow-up at 6 weeks to assess efficacy/adherence (SIGN 122).

🔆 Special Topical Guidance

• 🧴 Scalp psoriasis: Potent corticosteroid short-term ± vitamin D analogue (SIGN 121).
• 🔄 Flexural psoriasis: Moderate steroids short-term. Alternatives: tacrolimus, vitamin D analogues.

🌞 Phototherapy & Systemic Therapies

• 🌞 Phototherapy: Narrow-band UVB for widespread guttate or resistant psoriasis.
• 💊 Oral retinoids: Acitretin for severe disease.
• 🛡️ Immunosuppressants: Ciclosporin, methotrexate, mycophenolate.
• 🧬 Biologics: Infliximab, etanercept, adalimumab, ustekinumab for severe refractory psoriasis.
• ⚠️ Systemic corticosteroids: Reserved for emergency pustular/erythrodermic cases → risk of rebound flare.

📈 Prognosis

• Chronic, relapsing condition with variable severity.
• Good control possible with modern therapies.
• Important to monitor for psoriatic arthritis + metabolic/cardiovascular comorbidities.

📚 References

• SIGN 121: Psoriasis & Psoriatic Arthritis
• WHO: Psoriasis
• NCBI Bookshelf: Psoriasis
• Merck Manual
• AAFP: Psoriasis Diagnosis & Management