Psoriasis
- Thought to be an autoimmune skin disease with inherited genetic predisposition & immunological triggers
- PSORS1 on chromosome 21 within MHC has been identified
- HLA-CW6 in 60%; HLA -B17, -CW6, -DR4 & -DR7 a/w psoriatic arthropathy
- Immunological stimuli (eg. B-hemolytic streptococci & drugs (eg. antimalarials))
- Alcohol increases incidence and makes it more intractable
- Smoking is a/w palmoplantar pustulosis
Clinical
Features
when the scale of psoriasis is gently scraped it comes off easily, revealing dilated blood vessels underneath (will bleed)
- Rare but serious and even life threatening
- Sheets of small, sterile yellowish pustules develop on an erthematous background and may spread rapidly. Pustules may coalesce into lakes of pus
- Onset is acute
- Patient is unwell with high, swinging fever and leukocytosis
- Patient may die often of secondary infection
Management
Topical
Systemic
- Phototherapy & Photochemotherapy
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- In mild/moderate chronic plaque psoriasis
- Calcipotriol (Dovonex) up to 100g/week BD, scalp preparation
- Tacalcitol (Curatoderm) ointment up to 35g/week OD on scalp & face
- calcitriol (Silkis)
- Often used in alternation with topical steroid or in combination with UVB or PUVA therapy
- Adv: do not smell/stain, easy to apply & no risk of skin atrophy
- Disadv: skin irritation, possible hypercalcaemia if exceeds maximum dose
UVB
- 290 – 320 nm given 3 times a week
- Can be given to children or pregnant women
- Combined with other topical agents
- Main SE: acute sunburn & increased long-term risk of skin cancer
- For face, genitalia, flexures and for stubborn plaques on hands, feet & scalp
- Potent ones should not be applied to the face
- Adv: clean, non irritant, easy to use
- Disavd: skin atrophy, induction of acne/dermatitis, atypical fungal infection, systemic absorption, tachyplaxis
Psoralen plus UVA (PUVA)
- 8-methoxypsoralen PO before UVA (320 – 400nm)
- Causes cross-linkage in DNA, inhibits cell division & suppresses cell-mediated immunity
- Immediate SE: pruritus, nausea, mild erythema
- Long term: increased risk of skin cancer, premature skin ageing, cataracts (use UVA-opaque sunglasses for 24h after taking psoralen
- Useful in inpatient care eg: combined with UVB (Goeckerman regiment)
- Outpatient: refined tar (1 -10%)in cream or lotion base eg: Alphosyl, Carbo-Dome, Exorex
- Suitable for chronic plaque psoriasis/ guttate psoriasis after the acute phase
- Adv: safe, act by inhibiting DNA synthesis
- Disadv: smelly and messy
- Folate antagonist
- May have anti-inflammatory + immune modulatory effects
- Given once a week PO in single dose (7.5 – 15 mg)
- Prior: liver, kidney, bone marrow functions must be assessed
- Improvement is within 2 – 4 weeks
- C/I: liver disease, alcoholism, acute infection
- After administration, liver function is monitored either with serum procollagen III aminopeptide or liver biopsy
Inpatient
- Adv: antimitotic efect
- Disadv: irritant to normal skin, stains on skin, hair, linen, clothes & bathtubs --> purple- brown colour
- usually used with Lassar’s paste (zinc & salicyclic acid paste)
- Applied to plaques initially 0.1%, up to 2%
- Surrounding skin is prepared with bland preparation eg: white soft paraffin.
- Treated area is covered with tube gauze
- Ingram regimen: combined with daily tar bath & UVB. Psoriasis usually clears within 3/52
- Dithranol is applied 30 min each day in stable plaque psoriasis
- Wash off with shower
- Dithrocream (0.1% - 2%)
Outpatient
- Vitamin A derivative acitretin (Neotigason) – effective in pustular psoriasis & thinning hyperkeratotic plaques
- May be used with topical agents or UVB or PUVA
- Minor SE: dry mucosa, itching, peeling of skin
- Serious SE: hyperostosis, abnormal LF, hyperlipidaemia, teratogenicity
- Topical: tazarotene(0.05% & 0.1% Zorac gel)
- Effective for chronic plaque psoriasis
- May irritate, often used in alternation with topical steroid
- Neoral, an immunosuppressant is effective in severe psoriasis.
- Inhibits T-lymphocyte activation & IL-2 production
- SE: dose-dependent reversible nephrotoxicity. BP & kidney function are monitored during treatment
- Risk of skin cancers or lymphoma. Avoid concomitant UV treatment
- Keratolytics & Scalp preparations
- Hydroxyurea: does not affect liver function but suppresses bone marrow
- Fumaric acid esters are effective in some cases
- Other biologic agents are expensive
- 5% salicyclic acid ointment: hyperkeratotic psoriasis of palms & soles
- 3% salicyclic acid in cream base: scalp psoriasis applied daily or once in 2-3 days, combined with a tar-containing shampoo eg: Alphosyl, Capasal, Polytar, T/Gel).
- Coconut oil compound eg Cocois also helps scaly scalps
due to inflammatory polymorphs infiltrating the epidermis
Well-defined raised areas of psoriasis
May be very prominent
Plaques appear thickened with masses of adherent and shedding waxy appearance
Scratching produces waxy appearance - tache de bougie
due to widespread dilated cutaneous blood vessels
Redness of affected skin very marked, especially at flexures.
Erythrodermic psoriasis - >90% of body surface
Commonly seen in palmoplantar psoriasis where deep-seated pustules are dominant features.
Rarely on trunks and limbs (unstable psoriasis)
Normal - keratinocytes migrate from basal layer of epidermis to surface in
23 days
Psoriasis - process takes 3-5 days => thickened skin due to scaling
Lifting of the nail plate off the nail bed
due to abnormal nail adhesion
usually manifests as a white/salmon patch on the nail plate
accumulation of chalky-looking material under the nail
due to excessive proliferation of the nail bed (can => onycholysis)
very small depression in the nail plate
result from parakeratotic cells being lost from the nail surface
Complications
Transverse lines on the nail plate
due to intermittent inflammation of the nail bed leading to transient arrest in nail growth
due to leakage of blood from dilated tortuous capillaries
Depending on the type and location of the psoriasis and how widespread the disease is, psoriasis can cause complications. These include:
pruritus, fissuring, bleeding of lesions
- in generalized pustular or erythrodermic psoriasis:
- fever, weight loss
- congestive heart failure (due to increased cutaneous blood flow)
- fluid/electrolyte imbalance
- hypoalbuminemia, low iron, hyperuricemia
- patients with psoriasis often feel stigmatized and socially isolated
- loss of self-esteem
- depression
- costs of medication
- time away from work
Aetiology
- 5-10% of patients with psoriasis will have psoriatic arthritis;
- seronegative (RF), association with HLA-B27
- asymmetric peripheral joint involvement (most common)
- symmetric peripheral joint involvement (resembles rheumatoid arthritis)
- axial disease (resembles ankylosing spondylitis)
- arthritis mutilans (uncommon)
Chronic, non-infectious, inflammatory
dermatosis characterised by well-demarcated
erythematous plaques topped by silvery scales
Increased T-cell activity in skin
Types
Increased levels of proinflammatory cytokines in psoriatic lesions (esp. gamma-INF and TNF-alpha
Increases keratinocyte proliferation
+
Induces SKALP/elafin gene
marker for abnormal keratinocyte differentiation, hyperproliferative epidermis and increased inflammation
- Most common pattern
- Single or multiple well defined,raised disc shaped plaques involving the elbows, knees, scalp hair margin or sacrum
- Plaques usually red and covered by waxy white scales. If detached, may leave a bleeding points (Auspitz sign)
- An acute symmetrical eruption of “drop like” lesions with little scale in the early stage, usually on the trunk and limbs
- Mostly occurs in adolescents or young adults
- May follow a streptococcal infection
References
- Buxton PK, Morris-Jones R. "ABC of Dermatology". BMJ books; Wiley-Blackwell; 5th edition; 2009.
- Gawkerodger. "Dermatology: An Illustrated Colour Text". Churchill Livingstone; Elsevier; 4th edition; 2008.
- http://www.mims.co.uk/news/882277/Psoriasis/
- Affects the axillae, submammary areas, umbilicus, groin and natal cleft
- Plaques are smooth,often glazed and itchy
- Mostly found in elderly
Epidemiology
characterized by yellow to brown coloured sterile pustules on the palms and soles. Most common in middle aged woman who are cigarette smokers
uncommon indolent type of pustulosis affecting the digits and nails.
- Acrodermatitis of Hallopeau
very common, indeed scalp may be affected alone. May be confused with dandruff + seborrhoiec dermatitis but is generally better demarcated and more thickly scaled
well defined psoriasiform eruption in the nappy area of infants. Few develop true psoriasis later in life
- Affects 3% of the Malaysian Population
- partly hereditary and partly brought on by trigger factors in the environment (stress, certain infections, drugs, physical injury)
- individuals between the ages of 15 and 35, but can develop at any age. Approximately 10-15 percent of those with psoriasis get it before age ten.
- Unusual for children under the age of 8.
- Equal sex distribution
- Psoriasis affects the matrix or nail bed in 25-50% of cases
- 2 common findings: pitting and onycholysis
- Frequently associated with psoriatic arthropathy
- Treatment is difficult
Dermatological Society of Malaysia: http://www.dermatology.org.my/overview_psoriasis.html