Psoriasis Flashcards
Prevalence of psoriasis
0.5-3% of population
Aetiology
Unknown cause.
Can be genetic, may skip a generation.
Environmental factors trigger- stress, infection, medication.
When is the onset of psoriasis?
Onset usually early adulthood or middle aged.
More severe and harder to treat if diagnosed early adulthood.
Can occur in infants (nappy psoriasis), more red than nappy rash, doesn’t respond to usually nappy rash treatment.
What precipitates flare ups?
Sunburn, calcium deficiency hormonal factors.
Medications which can cause it?
Lithium, ß-blockers, IFN-alpha, withdrawal from systemic or potent topical corticosteroids, hydroxychloroquine.
Signs of Psoriasis
Well defined, raised, erythematous plaque with silver scale.
Bright red if acute.
Dusky if chronic.
NO VESICLES.
More scale and thicker skin in dryer areas.
Erythema predominate in moister areas.
Symptoms
Can be asymptomatic.
Itch to some degree common, esp if acute phase. More mild than eczema.
Affected Areas
Most common in flexures, head and groin.
Common on most of body.
Uncommon on hands and feet.
Rare on face.
Medications used
Start with Keratolytics and emollients Tars Topical steroids Vitamin D analogues Retinoids Antibiotics (Guttate form, Strep URTI can precipitate) Phototherapy, methotrexate, cyclosporin Biologicals.
Emollients
Soothe scaling and irritation
Keratolytics
Soften and lift scale.
Salicylic Acid 2-10%
Tars
Anti-inflammatory and antipruritic.
Coal Tar 2-10% ± salicylic acid 2-6%.
Sticky and smelly, people don’t like this.
Dithranol
Antiproliferative 0.1-2% ± salicylic acid.
Stains skin-transient.
Stains cloth permanently.
May burn unaffected skin- not for use on face, flexures or groin-sensetive areas.
Long contact, once daily 0.1-2%
Short contact, once daily for 10-30mins 0.5-5%.
Wash hands, wear old clothes, use old sheets etc.
Topical Corticosteroids
Ointment based.
More potent to treat thicker skin.
Pulse treatment, 1 month on 1 month off to minimise tachyphylaxis and adverse effects.
Vitamin D analogues
Calcipotriol.
Regulate proliferation and differentiation of keratinocytes.
Takes 6 weeks to reach peak effect, slow working.
0.005% BD, using too much 100mg/week may cause hypercalcaemia.
SE- erythema and irritation esp to sensitive areas, can use with corticosteroid.
Topical Retinoids- Vitamin A analouges
Tazarotene-
Can be used with corticosteroids due to local irritation, plus a synergistic effect.
0.05-0.1% crm.
Causes photosensitivity.
Methotrexate
Inhibits dihydrofolate reductase. Slows epidermal cell proliferation.
0.2-0.4mg/kg once a week.
Monitor FBC, renal and liver func.
ADRs- nausea, pancytopenia (prone to infection), elevated liver enzymes. Use folic acid to reduce effects but not on the same day.
Sig DIs- reduce efficacy or increase toxicity.
Cyclosporin
1-2.5mg/kg BD.
Not long remissions once stop taking it.
Not recommended for long term use due to ADRs- hypertension, deterioration of renal function, hirsutism, gingival hyperplasia and neoplasia (skin cancer, lymphoma).
Significant DIs.
Systemic retionoids
Acitretin
regulate cell proliferation and differentiation, anti-inflammatory.
Used for severe psoriasis, palm, plantar and pustule.
0.5mg/kg daily.
Increases the efficacy of phototherapy.
Combo with topical agents.
Avoid in pregnancy and 2yrs after.
ADRs- hypervitaminosis A, chelitis, hair shedding, photosensitive, elevated liver enzymes.
Biologicals
Last resort, target pro-inflammatory cytokine TNF-alpha, (etanercept, adalimumab, infliximab, ustekinumab).
IM, SC. Variable response, if works is dramatic.
May improve associated arthritis.
Well tolerated may reactivate latent infection (TB) or induce malignancy.
High benefit but high risk.
Phototherapy
Controlled exposure to UV radiation. Broadband UVB (290-320nm) Narrowband UVB (311nm) UVA (320-400nm) Use Methoxsalen/acitretin (oral/topical) to increase the photosensitivity which enhances treatment. Narrowband UVB becoming 1st line.
