Definition - Chronic inflammatory skin disease
- Characterised by erythematous, circumscribed scaly papules, and plaques on elbows, knees, extensor limbs, scalp, and, less commonly, nails, ears, and umbilical region
- Typically lifelong, with a fluctuating course of exacerbations and remission.
- Causes itching, irritation, burning, and stinging in half the cases
Risk Factors - Genetic
- Linked to the class I and II major histocompatibility complex on human chromosome 6.
- Genetic foci found to be associated with psoriasis include PSOR1 and PSOR2.[9] [10]
- Immune response
- Associated with increased activity of T cells in underlying skin.
- Biological agents used to treat severe psoriasis directly modify the function of T cells
- HIV-positive patients develop more severe psoriasis. [10][11] [12]
- Infection
- Guttate psoriasis is observed to follow an upper respiratory infection, such as streptococcal pharyngitis, and is believed to be an infection-induced disease.
- Viral infection and immunisation have also been linked to the flare of psoriasis. [10] [13]
- Stress
- Stress aggravates the occurrence of psoriasis and makes psoriasis worse.
- Stress reduction techniques may be useful in controlling psoriasis. [15] [16]
- Trauma
- Trauma, such as surgical scars and injection sites, may result in the appearance of new psoriatic lesions at the sites of injury. [17]
- Smoking
- Smokers have a higher risk of psoriasis.
- This has been documented in several population studies.
- In one study the risk of having psoriasis was 1.7 to 1.9 times more likely in former or current smokers.
- The risk of having pustular psoriasis was even higher at 5.3 times. [16]
Differential diagnosis Epidemiology - The incidence of psoriasis is around 60 per 100,000 people[2]
- In general, about 1.5% to 3.5% of the white population has psoriasis. [3]
- The mean age of onset is 28 years, with equal distribution between men and women. [4]
- Asian populations appear to have a very low prevalence of psoriasis (0.3%). [5]
- The incidence of psoriatic arthritis is 1.4 per 100,000 and a prevalence of 24 per 100,000
- this is a conservative figure including only those with significant arthritis [6]
- Another estimate suggests an incidence of 6.6 per 100,000 and a prevalence of 100 per 100,000. [7]
- Around 7% to 11% of psoriatic patients have arthritis. [2] [7] [8]
Aetiology - The aetiology is unknown. Several factors have been suggested:
- Immunology
- Psoriasis appeared after cessation of systemic corticosteroids (rebound)
- It is aggravated by the use of anti-malarials, lithium, and beta-blocker drugs
- Lesions of psoriasis are associated with increased activity of T cells in underlying skin
- Biological agents used to treat severe psoriasis directly modify the function of T cells
- HIV patients have more severe and frequent psoriasis. [10] [11] [12]
- Infection
- Guttate psoriasis is observed to follow an upper respiratory infection, such as streptococcal pharyngitis
- Viral infection and immunisation have also been linked to the flare of psoriasis. [10] [13]
Clinical features - Skin lesions
- Typically erythematous, circumscribed scaly papules and plaques
- On elbows, knees, extensor surfaces of limbs, scalp, and, less commonly, nails, ears, and umbilical region
- Typically blanching
- In plaque psoriasis, there are raised inflamed plaque lesions with a superficial silvery-white scaly eruption
- The scale may be scraped away to reveal inflamed and sometimes friable skin beneath
- In guttate psoriasis, there are widespread, erythematous, fine, scaly papules (water drop appearance) on trunk, arms, and legs.
- The lesions often erupt after an upper respiratory infection. [1]
- In pustular psoriasis, (von Zumbusch) there are sterile pustules on the hands and feet
- Diffuse or circular erythematous lesions with pustules and scaling on the trunk. [1]
- In erythroderma (erythrodermic psoriasis), there is generalised erythema with fine scaling.
- It is often associated with pain, irritation, and sometimes severe itching. [1]
- Auspitz's sign is the appearance of punctate bleeding spots when psoriasis scales are scraped off, named after Heinrich Auspitz
- FHx
- Light skin
- Psoriasis is around twice as common in white populations as in black people
- Skin discomfort
- Skin is highly sensitive and itching can be severe.
- Bleeding may occur if the lesions are scratched.
- The skin can be painful, particularly if joints are involved
- Smoking
- Smokers are at higher risk of psoriasis.
Pathophysiology - Psoriasis is a hyperproliferative disorder, involving a complex cascade of inflammatory mediators
- Mitotic activity of basal and suprabasal cells is significantly increased, with cells migrating from the basal layer to the stratum corneum in just a few days
- The silver scale on the surface of psoriasiform lesions is simply a layer of dead cells. [10] [14]
- Cytokines, particularly proinflammatory cytokines, T cells, macrophages, and vascular endothelial growth factor are heavily involved in pathogenesis
- Tumour necrosis factor-alpha (TNF-alpha), in particular, has been a target of biological therapy.
- TNF-alpha is high in serum, synovium and psoriatic plaques.
- Human monoclonal antibodies that block TNF-alpha receptors, or inhibit binding or activation of TNF-alpha receptors, have been shown to significantly control psoriasis
Investigations- Skin biopsy
- Intraepidermal spongiform pustules and Munro neutrophilic microabscess within the stratum corneum
- In addition to these classical features, others include focal parakeratosis and epidermal acanthosis with dilated capillaries within dermal papillae.
- Skin biopsy should be ordered only when diagnosis is in doubt, but biopsy does not always show classic pathological features.
Management a) conservativeb) medical - Emolients
- Ointments (such as Aquaphore) or thick creams (such as Cerave, Nivea, or Eucerin) that are used to reduce scale and irritation. [22]
- They are available as over-the-counter preparations and should be applied at least once a day, preferably twice a day, but can be applied more often if required
- Although both preparations are effective, most patients prefer creams to ointments, and compliance tends to be better with cream preparations.
- Topical corticosteroids
- Generally, the lowest potency of topical corticosteroid should be used.
- This often means a mid-potency agent for adults and most body areas.
- Low-potency treatments are appropriate for lesions on the face or intertriginous areas or for infants.
- High-potency topical corticosteroids are usually reserved for adults requiring short-term treatment of thick plaques that are resistant to lower-potency agents. [19]
- Topical vitamin D analogues
- Agents such as calcipotriol bind with vitamin D-selective receptors
- Have been shown to inhibit the hyperproliferation and abnormal differentiation of keratinocytes characteristic of psoriatic lesions. [19]
- These agents do not smell or stain clothes and may be more acceptable than tar or dithranol products.
- Calcipotriol has a relatively slow onset of action and its maximal effect is after 6 to 8 weeks
- For patients with scalp psoriasis, combination preparations consisting of a topical vitamin D analogue and corticosteroid (calcipotriene plus betamethasone dipropionate) are a welcome addition to the available topical therapies. [35]
- Oral retinoids
- These drugs (e.g., acitretin) are moderately effective in many cases and are often combined with other treatments.[C Evidence]
- Treatment is not recommended for >6 months.
- Liver function and blood lipid concentration should be monitored.
- Women of childbearing ages are not suitable for this regimen as retinoid agents are teratogenic.
- Methotrexate
- Folic acid antagonist and works as an antiproliferative and anti-inflammatory agent.[C Evidence]
- Although effective in most patients, it has the potential for hepatotoxicity. [24]
- Methotrexate is contraindicated in the following groups:
- pregnant patients; people with renal impairment, hepatitis, or cirrhosis;
- people who abuse alcohol;
- unreliable patients;
- patients with leukaemia or thrombocytopenia
- Folic acid may be used in addition to methotrexate to minimise adverse effects (such as GI symptoms).
- Dithranol cream
- Ciclosporin
- An effective treatment for psoriasis but has significant adverse effects.[C Evidence]
- Long-term use (i.e., >12 months) is not recommended.
- A break (i.e., drug vacation) is recommended after 1 year, switching to other drugs such as methotrexate.
- Ciclosporin can then be restarted
- Biological agents
- Newer biological therapies are recommended as possible treatment
- if the psoriasis is very severe and the disease has not improved with other treatments such as ciclosporin, methotrexate, or PUVA,
- or the patients have had adverse effects with these in the past, or such therapy is contraindicated. [24]
- Alefacept
- Has a dual mechanism of action that involves induction of T-lymphocyte apoptosis and interruption of T-lymphocyte activation.[A Evidence]
- Etanercept
- Inhibits tumour necrosis facto-alpha (TNF-alpha), an important cytokine involved in the pathogenesis of psoriasis
- Has been shown to significantly reduce the severity of plaque psoriasis.[A Evidence]
- Furthermore, etanercept has been demonstrated effective in treating psoriasis in adults, children, and adolescents.[25]
- Infliximab
- Also inhibits the activity of TNF-alpha and has been shown to have efficacy in the treatment of chronic plaque psoriasis
- It has also been demonstrated to improve health-related quality of life in patients with psoriasis. [28]
- Meta-analysis has demonstrated that infliximab is more effective than adalimumab and etanercept. [29]
- Adalimumab
- Inhibits the activity of TNF-alpha and has been shown to have efficacy in in the treatment of chronic plaque psoriasis. [30] [31]
- It is more effective than methotrexate and placebo. [32]
- Studies have demonstrated improvement in health-related quality of life. [33]
- Ustekinumab
- Humanized monoclonal antibody
- Inhibits Interleukins 12 and 23.
- It has been shown to be effective in clinical trial for psoriasis. [34]
- Retinoid-PUVA (re-PUVA)
- The re-PUVA regimen consists of methoxsalen and ultraviolet A (PUVA) with an oral retinoid
- May prevent antigen presentation process by Langerhans cells in the skin
- Acitretin is given the day before PUVA therapy, which enhances the efficacy.
- Adverse features include inconvenient scheduling (treatment is delivered 3 to 5 times per week), phototoxicity (during and after treatment), and burning if the dose is not adequately controlled
c) surgicalPrognosis |
