Dermatology
Psoriasis
Library·Dermatology·Psoriasis
Don't miss
- Psoriatic arthritis - affects up to 30%; screen at every visit (joint pain, dactylitis, nail pitting)
- Erythrodermic or pustular psoriasis with systemic features - admission
- Cardiovascular and metabolic comorbidity - psoriasis is independent CV risk
- IBD and depression - both raised in psoriasis
First-line
- Severity
- BSA + DLQI; small but high-impact site (face, palms, genitals) is "moderate"
- Mild
- Daivobet (calcipotriol + betamethasone) - PHARMAC-funded, highly effective for body and scalp
- Scalp
- Daivobet gel or coal tar shampoo + potent steroid lotion
- Moderate-severe
- Refer for phototherapy or biologic (IL-17, IL-23, TNF inhibitors funded with criteria)
Refer when
- BSA ≥10% or DLQI >10 despite optimised topicals
- Difficult sites significantly impacting life
- Suspected psoriatic arthritis - rheumatology
- Pregnancy planning on systemic therapy
Tell the patient
- Psoriasis is lifelong but very treatable - the goal is control, not cure
- Triggers: stress, infection, alcohol, smoking, beta-blockers, lithium
- Treat associated CV risk and mood as part of the condition
- Joint pain or stiffness lasting >30 minutes in the morning is worth telling us about
Psoriasis affects approximately 2-3% of the New Zealand population.1 It is a lifelong condition with a relapsing-remitting course, driven by dysregulated T-cell activity leading to accelerated keratinocyte proliferation. Beyond skin involvement, it carries significant comorbidity burden: psoriatic arthritis, cardiovascular disease, metabolic syndrome, depression, and inflammatory bowel disease all occur at higher rates than in the general population.2
❍ Severity assessment
Two parameters matter: body surface area (BSA) and quality-of-life impact (Dermatology Life Quality Index, DLQI).
- Mild: BSA under 3% and DLQI ≤10. Manage in primary care with optimised topicals.
- Moderate-to-severe: BSA ≥10%, or DLQI >10, or involvement of difficult sites (face, hands, feet, genitalia, nails, scalp). Refer for phototherapy or systemic/biologic therapy.
The DLQI is worth using. A patient with 5% BSA involvement but severely affected sleep, social life, and work capacity has moderate-to-severe disease by functional classification. Quality of life drives the referral decision as much as extent.
Difficult sites warrant earlier consideration of referral regardless of BSA: palmoplantar psoriasis (hands and feet) is functionally disabling; facial and scalp psoriasis is visible and psychologically burdensome; nail psoriasis (pitting, onycholysis, subungual hyperkeratosis) is often treatment-resistant. Genital psoriasis is underreported and underdiagnosed - it warrants specific enquiry and appropriate management.
Calculators PREDICT-CVD 5-year cardiovascular risk for NZ patients, with Framingham, QRISK3, SCORE2, and ACC/AHA for comparison. Stroke risk in atrial fibrillation and anticoagulation decision support. Weight- and age-based dosing aligned to NZFc and Starship guidelines. Alcohol (AUDIT), cannabis, and nicotine/vaping risk profiles with evidence-based harm summaries and cessation guidance. Tapering schedules and cross-tapering transitions. Covers SSRIs, SNRIs, TCAs, and mirtazapine. Filterable reference for 22 agents: NZ dosing, side effects, CYP450, cost, and pregnancy safety by indication and class. Diazepam-equivalent conversion for 11 agents including Z-drugs. Switching protocols and dependence management. GP-relevant medicines with PHARMAC funding status, prescriber requirements, and NZ dosing. Filterable by category, funding, and prescriber type. Conversion across 9 opioid agents including transdermal patches. Aligned to NZ HealthPathways guidance. Glucocorticoid potency and dose comparison (prednisolone equivalent). Medicines prescribed overseas that are unavailable, unfunded, or differently restricted in NZ -- with local equivalents. Cumulative ACB score across a patient medication list, with STOPP flags and deprescribing guidance. FRAIL, Katz ADL, Lawton IADL, and Rockwood CFS for frailty and functional assessment. BPAC/GOLD-staged medication selector with NZF-subsidised inhaler options. Naegele rule and gestational age by LMP or ultrasound. Kamath and Stothard six-item weighted score for CTS probability.
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