Psoriasis is a chronic inflammatory skin condition.
In its most common form it consists of thick, scaly plaques that are pinkish red in colour and tinged with a silvery white scale. The commonest sites affected are the scalp, outer surface of knees and elbows. However, there are several other types. It can present at any age, including in childhood, however most cases occur between 15-25 years and 50-60 years of age. Psoriasis is associated with several other medical conditions including obesity, cardiovascular disease, Type 2 Diabetes and also other inflammatory conditions including arthritis and coeliac disease.
It poses a significant burden both physically and psychologically as it can be difficult to treat.
Genetic factors: these play a large part; 30% of people with one first degree relative affected will go on to develop the condition. If two relatives are affected, this rises to approximately 60 %
Lifestyle factors: Psoriasis is more common in people with Metabolic Syndrome, this is an umbrella term used to group together conditions that are closely related, such as obesity, high blood pressure, Type 2 Diabetes, and high cholesterol. Smoking and alcohol are also thought to be risk factors. Stress can also trigger and exacerbate psoriasis.
Drugs: some drugs can trigger psoriasis; others can make the condition worse. In the first situation, the condition is likely to resolve completely on discontinuation of the drug, in the second this is increasingly unlikely to happen.
Our understanding of psoriasis is improving. We know that it is caused by accelerated growth of cells in the top layer of the skin, the epidermis. Normally they would regenerate every 28 days but in this condition this occurs every 2-4 days, causing the characteristic plaques. Inflammation of the skin also occurs, although what drives this process is still unclear. We can target treatments against these causative factors, with a wide array of therapies available. Currently, however, there is no cure or single treatment that is guaranteed to work.
Weight loss, reduction in alcohol consumption and stress levels, smoking cessation and blood pressure control can improve the condition.
Certain drugs which may either induce or provoke psoriasis should be avoided. These include Beta blockers, antimalarial tablets, Lithium, Nonsteroidal Anti- Inflammatory drugs, and some antibiotics.
Sun exposure tends to dramatically improve Psoriasis by having an anti-inflammatory effect on the skin. Exposure should be limited to 30 minutes at a time. Care should be taken to avoid the hottest times of day (12pm-2pm) and to use a sunscreen with an SPF of at least 30. This is both to reduce the risk of developing skin cancer and because sunburn can cause psoriasis to flare.
An observational study published by JAMA Dermatology found that people with psoriasis who followed a Mediterranean diet, that is one rich in fruits, vegetables, legumes, fish, wholegrains, and extra virgin olive oil experienced fewer flare ups. However, this was only an association, and more studies are needed.
There is no clear establishment of cause and effect, however, in a recent study published in 2019 in JAMA Dermatology, researchers found an association between Psoriasis and an increased risk of developing several cancers including oesophagus, kidney colon and larynx. However more studies are needed to look at lifestyle and other factors that may play a role. There is a more established link between psoriasis and non-melanoma skin cancers.
A good general regime for the treatment of chronic plaque psoriasis would be to use a soap substitute such as Aqueous cream or Aveeno Daily Moisturising Body Cleansing Oil followed by a bath additive such as Balneum Plus Bath Oil. After bathing, the generous application of an emollient is recommended. This softens the skin and adds moisture, improving the scaling and irritation. The regular use of emollients and moisturisers softens psoriasis and adds moisture to the skin. Aveeno Moisturising Cream would be one option, or for more scaly areas perhaps Diprobase Cream Emollient or Hydromol Ointment. It is important to note that emollients are often flammable so care needs to be taken near open flames; caution is also advised when stepping into the bath as they may be very slippery.
Several treatments may need to be tried before the best treatment regime can be ascertained, with different treatments sometimes being used at the same time, or in succession.
Further treatment of psoriasis will depend on severity of disease as well as disease type.
Psoriasis affecting the trunk and limbs.
The National Institute for Health Care and Excellence (NICE) recommends the use of a potent steroid for example Betnovate Cream or Mometasone furoate 0.1% once daily in the morning together with Calcipotriol (Vitamin D derivative) ointment in the evening for a period of four weeks as the initial treatment. The steroid works by reducing inflammation and the Calcipotriol reduces the overgrowth of skin cells and promotes formation of normal skin cells.
If this treatment is not effective, steroids and Vitamin D derivatives can be used in combination. These may be in the form of a cream such as Dovobet Cream or Dovobet Gel, or a foam preparation for example, Enstilar Cutaneous Foam, which may aid ease of application.
If steroids and Vitamin D derivatives do not work either alone or in combination, dithranol in the form of Dithrocream may be worth a try. This should not be applied on sensitive areas such as the face or on inflamed skin. The lowest strength cream should be applied (Dithrocream 0.25%) once a day and left on for 30-60 minutes before washing off, with weekly increases in strength if required. Treatment can be for up to 6 weeks. Dithranol can cause skin irritation, staining of skin and fabrics.
Coal tar products are another alternative. They are an effective treatment for psoriasis but have gone out of favour as they are messy to apply and have a distinctive odour and can cause staining of skin and clothes. Exactly how coal tar works is not understood but it appears to reduce inflammation, itching and normalise skin growth.
As a general rule, treatments should be reviewed at four-week intervals and potent steroids should not be used on the same area of skin for more than eight weeks at a time. Treatments can be repeated if needed after a break of four weeks.
This presents with a flaky redness with presence of scale. Common at the nape of the neck.
A coal tar shampoo such as Polytar Scalp Shampoo may be sufficient to treat mild cases. In more severe cases this may need to be combined with a steroid scalp application for example Betacap Scalp Application or Bettamousse Foam Mousse. Other possibilities include Dermovate Scalp Application and Etrivex Clobetasol Medicated Shampoo. It may also be worth using an agent to remove scale containing Salicylic acid such as Diprosalic Scalp Application. Vitamin D derivatives such as Calcipotriol scalp application can also be used either on their own or in combination with steroids.
Psoriasis of the face, flexures and genitals.
In the flexures (skin folds) this often appears red and shiny with no scaling. On the face redness is present with fine white flakes, scaling may be present.
This should be treated with a mild or moderately potent steroid such as 1% Hydrocortisone or Eumovate Cream for 1-2 weeks. Treatment can be repeated, so long as steroids are not used for more than 2 weeks each month. Steroid treatment should not be on a continuous basis as it can cause thinning of the skin. If there is danger of this occurring, it is worthwhile trying a Calcineurin inhibitor such as Protopic ointment. This should be prescribed by a doctor experienced in treating psoriasis.
This is the rapid development of raindrop type red plaques over the limbs, chest and trunk. It usually follows a throat infection by a bacteria called Streptococcus Pyogenes. Treatment is not always needed, as often it resolves naturally within 3-4 weeks. The same treatments that are used for plaque Psoriasis can be used, however steroid creams should only be used to treat localized areas.
Then a specialist assessment is needed by a Consultant Dermatologist who may consider phototherapy, strong oral medications such as Methotrexate or Acitretin or biological agents such as Adalimumab. All of these require very careful monitoring.
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