Psoriasis

Question 1

Prevalence of psoriasis

Answer 1

0.5-3% of population

Question 2

Aetiology

Answer 2

Unknown cause.
Can be genetic, may skip a generation.
Environmental factors trigger- stress, infection, medication.

Question 3

When is the onset of psoriasis?

Answer 3

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.

Question 4

What precipitates flare ups?

Answer 4

Sunburn, calcium deficiency hormonal factors.

Question 5

Medications which can cause it?

Answer 5

Lithium, ß-blockers, IFN-alpha, withdrawal from systemic or potent topical corticosteroids, hydroxychloroquine.

Question 6

Signs of Psoriasis

Answer 6

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.

Question 7

Symptoms

Answer 7

Can be asymptomatic.

Itch to some degree common, esp if acute phase. More mild than eczema.

Question 8

Affected Areas

Answer 8

Most common in flexures, head and groin.
Common on most of body.
Uncommon on hands and feet.
Rare on face.

Question 9

Medications used

Answer 9

Start with 
Keratolytics and emollients
Tars
Topical steroids
Vitamin D analogues
Retinoids
Antibiotics (Guttate form, Strep URTI can precipitate)
Phototherapy, methotrexate, cyclosporin
Biologicals.

Question 10

Emollients

Answer 10

Soothe scaling and irritation

Question 11

Keratolytics

Answer 11

Soften and lift scale.

Salicylic Acid 2-10%

Question 12

Tars

Answer 12

Anti-inflammatory and antipruritic.
Coal Tar 2-10% ± salicylic acid 2-6%.
Sticky and smelly, people don’t like this.

Question 13

Dithranol

Answer 13

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.

Question 14

Topical Corticosteroids

Answer 14

Ointment based.
More potent to treat thicker skin.
Pulse treatment, 1 month on 1 month off to minimise tachyphylaxis and adverse effects.

Question 15

Vitamin D analogues

Answer 15

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.

Question 16

Topical Retinoids- Vitamin A analouges

Answer 16

Tazarotene-
Can be used with corticosteroids due to local irritation, plus a synergistic effect.
0.05-0.1% crm.
Causes photosensitivity.

Question 17

Methotrexate

Answer 17

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.

Question 18

Cyclosporin

Answer 18

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.

Question 19

Systemic retionoids

Answer 19

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.

Question 20

Biologicals

Answer 20

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.

Question 21

Phototherapy

Answer 21

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.