Psoriasis: 6 Types, Symptoms, And Treatment Options
Chronic inflammatory skin condition with red, scaly plaques: causes, types, diagnosis, and comprehensive treatment options.
Psoriasis is a
chronic inflammatory skin condition
characterised by clearly defined red plaques with silvery scales, often itchy or sore. It affects approximately 2–3% of the population and can significantly impact quality of life.What is psoriasis?
Psoriasis arises from rapid turnover of skin cells, leading to accumulation of immature keratinocytes forming thick, scaly plaques. It is a multifactorial disease involving genetic predisposition, immune dysregulation (T-cell mediated), and environmental triggers. Histologically, it shows parakeratosis, acanthosis, absent granular layer, and inflammatory infiltrate.
Who gets psoriasis?
Psoriasis affects all ages, races, and both sexes equally. Peak onset is bimodal: 20–30 years and 50–60 years. Family history increases risk; 30% have affected relatives. Higher prevalence in Caucasians.
Types of psoriasis
- Chronic plaque psoriasis (80–90%): Most common, thick plaques on elbows, knees, scalp, lower back.
- Guttate psoriasis: Small drop-like lesions, often post-streptococcal infection in children/young adults.
- Pustular psoriasis: Sterile pustules on erythematous base; generalised or palmoplantar.
- Erythrodermic psoriasis: Widespread redness, rare but severe.
- Flexural (inverse): Smooth red patches in skin folds.
- Scalp, nail, palmoplantar: Site-specific variants.
Causes of psoriasis
Genetic factors (e.g., HLA-Cw6 association) interact with triggers: streptococcal pharyngitis (guttate), trauma (Koebner phenomenon), drugs (beta-blockers, lithium), stress, smoking, alcohol, HIV. No single cause; immune activation leads to cytokine release (TNF-α, IL-17, IL-23).
Clinical features of psoriasis
Plaques are erythematous with white micaceous scale; Auspitz sign (pinpoint bleeding on scale removal), candle-grease sign. Itch, soreness common. Scalp psoriasis causes stubborn scale; nail pitting, onycholysis in 50%; palmoplantar hyperkeratosis/cracks.
Complications of psoriasis
- Psoriatic arthritis (10–30%): Joint pain, swelling; assess with history/exam.
- Metabolic syndrome: Obesity, diabetes, hypertension, dyslipidaemia.
- Cardiovascular disease: Increased risk due to chronic inflammation.
- Depression/anxiety: Quality of life impact.
- Severe forms: Dehydration, infection in erythroderma/pustular.
Diagnosis of psoriasis
Clinical diagnosis in most cases; biopsy rarely needed (shows regular acanthosis, parakeratosis, Munro microabscesses). Differential: eczema, tinea, lichen simplex, seborrhoeic dermatitis, cutaneous lupus. Assess severity with
PASI score
(Psoriasis Area and Severity Index): combines area (0–6 per region) and severity (erythema, induration, scale 0–4); total 0–72.| Body Region | Area Score (0–6) | Severity Multiplier (A=0.1, B=0.2, C=0.3, D=0.4) |
|---|---|---|
| Head/Neck | 0=none, 6=90–100% | 0.1 |
| Upper Limbs | 0–6 | 0.2 |
| Trunk | 0–6 | 0.3 |
| Lower Limbs | 0–6 | 0.4 |
PASI 75 = 75% improvement target.
Treatment of psoriasis
Treatment is tailored by type, severity, site, comorbidities. No cure; aim for clearance/remission. Mild (<3% BSA): topicals. Moderate (3–10%): topicals + phototherapy. Severe (>10%): systemic/biologics. Patient education essential.
General measures
- Emollients/moisturisers daily to hydrate, reduce scaling.
- Avoid triggers: alcohol, smoking cessation.
- Sunlight exposure cautiously.
Topical therapy (mild-moderate)
- Corticosteroids: Potent (clobetasol) for plaques; mild for face/flexures. Once/twice daily, 4 weeks max.
- Vitamin D analogues (calcipotriol, calcitriol): Reduce proliferation; combine with steroid.
- Coal tar: Shampoos/creams; irritant, odour.
- Dithranol: Short-contact for plaques; stains skin.
- Calcineurin inhibitors (tacrolimus): Face/flexures.
- Salicylic acid/urea: Keratolytics for scale.
- Novel topicals: Roflumilast (PDE4 inhibitor), tapinarof (AhR agonist) for plaques.
Phototherapy (moderate)
Narrowband UVB (NB-UVB) 2–3x/week; effective, safe short-term. PUVA (psoralen + UVA) for thicker plaques. Home UVB units possible.
Systemic non-biologic therapy (moderate-severe)
| Agent | Dose | Monitoring | Side Effects |
|---|---|---|---|
| Methotrexate | 7.5–25mg/week | LFTs, FBC, renal | Hepatotoxicity, nausea |
| Ciclosporin | 2.5–5mg/kg/day | BP, renal | Nephrotoxicity, HTN |
| Acitretin | 10–50mg/day | LFTs, lipids | Teratogenic, hyperlipidaemia |
Biologic therapy (severe/refractory)
Targets cytokines: TNF inhibitors (etanercept, infliximab), IL-17 (secukinumab, ixekizumab), IL-23 (guselkumab), IL-12/23 (ustekinumab). Subcutaneous/IV; rapid efficacy (PASI 90 often). Screen for TB, hepatitis; monitor infections.
Other
- Apremilast (PDE4 inhibitor oral).
- Avoid systemic steroids (rebound risk).
Psoriasis in specific sites
- Scalp: Shampoos (corticosteroid/coal tar), topicals under occlusion.
- Nails: Topicals poor; systemic/biologics best.
- Palms/soles: Potent topicals, acitretin, ciclosporin.
Psoriatic arthritis
Symmetric/asymmetric oligoarthritis, enthesitis, dactylitis, spondylitis. Screen with PEST questionnaire; early rheumatology referral. Methotrexate + biologics mainstay.
Assessment and outcome
Use PASI, DLQI (Dermatology Life Quality Index). Target: PASI 75–90. Relapse common; maintenance therapy. Multidisciplinary: dermatology, rheumatology, psychology.
Frequently Asked Questions
What causes psoriasis?
Genetic susceptibility plus triggers like infection, stress, injury. Immune overactivity drives skin cell hyperproliferation.
Is psoriasis contagious?
No, it is not infectious or contagious.
Can psoriasis be cured?
No cure, but treatments control it effectively long-term.
Does diet affect psoriasis?
Some benefit from gluten-free, low-alcohol, omega-3 rich diets; evidence limited.
What is the best treatment for mild psoriasis?
Topical corticosteroids + vitamin D analogues + emollients.
Are biologics safe?
Generally safe with screening; risk of infections, monitor regularly.
References
- Guidelines for the management of psoriasis — DermNet NZ. 2023. https://dermnetnz.org/topics/guidelines-for-the-treatment-of-psoriasis
- Treatment of psoriasis — DermNet NZ. 2024. https://dermnetnz.org/topics/treatment-of-psoriasis
- PASI (psoriasis area and severity index) — DermNet NZ. 2023. https://dermnetnz.org/topics/pasi-score
- Psoriasis overview — DermNet NZ. 2024. https://dermnetnz.org/cme/scaly-rashes/psoriasis-overview
- Psoriasis: Symptoms, Treatment, Images and More — DermNet NZ. 2025. https://dermnetnz.org/topics/psoriasis
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