Psoriasis

Introduction
Psoriasis is a chronic, immune-mediated inflammatory disease of the skin with systemic associations. It involves hyperproliferation of keratinocytes, abnormal differentiation, and an inflammatory infiltrate driven primarily by the IL-23/IL-17 and TNF-α pathways. It presents as well-demarcated erythematous plaques with silvery scales, and can also affect nails and joints. Management is guided by severity, distribution, comorbidities, and treatment response.

---

Epidemiology

• Affects ~2–3% of the population globally.

• Can occur at any age; peaks between 15–30 years (Type I, often familial) and 50–60 years (Type II, less genetic).

---

Types

1. Plaque psoriasis – Most common (80–90%).

2. Guttate psoriasis – Acute onset, often post-streptococcal.

3. Inverse psoriasis – Flexural areas.

4. Pustular psoriasis – Localized (palmar/plantar) or generalized (Von Zumbusch).

5. Erythrodermic psoriasis – Generalized erythema and scaling, potentially life-threatening.

6. Nail psoriasis – Pitting, onycholysis, subungual hyperkeratosis.

7. Psoriatic arthritis – Seronegative inflammatory arthritis in up to 30% of cases.

---

Treatment with Doses

1. Topical Therapy (Mild to Moderate Disease)

• Topical corticosteroids

  • Clobetasol propionate 0.05% cream/ointment: Apply thin layer to affected area once or twice daily for up to 2–4 weeks for thick plaques.

  • Betamethasone valerate 0.1%: Apply once or twice daily.

  • Reduce potency or frequency after improvement to avoid adverse effects.

• Vitamin D analogs

  • Calcipotriol 0.005% ointment/cream: Apply thinly to affected areas twice daily (max 100 g/week in adults).

  • Calcitriol 3 mcg/g ointment: Apply twice daily.

• Combination

  • Calcipotriol 0.005% + betamethasone dipropionate 0.064% ointment/gel: Apply once daily for up to 4 weeks.

• Coal tar

  • 1–5% preparations in ointment/shampoo: Apply daily; leave for 5–10 minutes on scalp before rinsing.

• Topical retinoids

  • Tazarotene 0.05%–0.1% gel/cream: Apply once daily at night; use with corticosteroid to reduce irritation.

---

2. Phototherapy

• Narrowband UVB: 2–3 sessions/week, dose individualized starting at ~70% of minimal erythema dose, increased gradually.

• PUVA: Oral methoxsalen (0.6 mg/kg) 2 hours before UVA exposure, 2–3 times/week.

---

3. Systemic Non-Biologic Therapy (Moderate to Severe Disease)

• Methotrexate

  • 7.5–25 mg orally or subcutaneously once weekly; adjust based on response and tolerance.

  • Supplement with folic acid 5 mg once weekly (day after methotrexate).

• Cyclosporine

  • 2.5–5 mg/kg/day orally in two divided doses; short-term use due to nephrotoxicity risk.

• Acitretin

  • 25–50 mg orally once daily with food; teratogenic, contraindicated in pregnancy (effective contraception during and for 3 years after discontinuation).

• Apremilast

  • Day 1: 10 mg AM; Day 2: 10 mg AM & PM; Day 3: 10 mg AM & 20 mg PM; Day 4: 20 mg AM & PM; Day 5: 20 mg AM & 30 mg PM; Day 6 onward: 30 mg orally twice daily.

---

4. Biologic Therapy (Moderate to Severe Psoriasis Not Controlled by Other Methods)

• TNF-α inhibitors

  • Etanercept: 50 mg subcutaneously twice weekly for 12 weeks, then 50 mg once weekly.

  • Adalimumab: 80 mg subcutaneously (Day 1), then 40 mg every other week starting Day 8.

  • Infliximab: 5 mg/kg IV at weeks 0, 2, and 6, then every 8 weeks.

  • Certolizumab pegol: 400 mg subcutaneously at weeks 0, 2, and 4, then 200 mg every 2 weeks.

• IL-12/23 inhibitor

  • Ustekinumab:

    • <100 kg: 45 mg subcutaneously at weeks 0, 4, then every 12 weeks.

    • ≥100 kg: 90 mg subcutaneously at weeks 0, 4, then every 12 weeks.

• IL-17 inhibitors

  • Secukinumab: 300 mg subcutaneously weekly for 5 weeks, then every 4 weeks.

  • Ixekizumab: 160 mg subcutaneously at week 0, then 80 mg every 2 weeks until week 12, then every 4 weeks.

  • Brodalumab: 210 mg subcutaneously at weeks 0, 1, and 2, then every 2 weeks.

• IL-23 inhibitors

  • Guselkumab: 100 mg subcutaneously at weeks 0 and 4, then every 8 weeks.

  • Tildrakizumab: 100 mg subcutaneously at weeks 0 and 4, then every 12 weeks.

  • Risankizumab: 150 mg subcutaneously at weeks 0 and 4, then every 12 weeks.

---

5. Psoriatic Arthritis Management in Psoriasis Patients

• NSAIDs for pain and stiffness.

• DMARDs such as methotrexate (7.5–25 mg/week) or leflunomide (20 mg/day).

• Biologics as above for refractory or severe joint disease.

---

Prognosis

• Psoriasis is chronic with remissions and relapses.

• Effective long-term control is possible with appropriate therapy, reducing both skin and systemic disease burden.