To ignore the impact of the condition on the patient’s life is to fail in treating psoriasis.
Like the Cheshire cat that Alice met, it tends to clear slowly and the last remaining patches are often the hardest to clear.
This is frustrating enough, but there is also the knowledge that it will probably recur and need further tedious courses of treatment, so encouragement and support are an essential part of treatment.
In an attempt to quantify the impact of psoriasis on the life of the individual patient the Psoriasis Disability Index (PDI) has been developed.
This takes the form of a questionnaire and covers all aspects of the patient’s work, personal relationships, domestic situation, and recreational activities.
It can be helpful in assessing the effectiveness of treatment as perceived by the patient.
Patients understandably ask whether psoriasis can be cured and often want to know the cause.
The cause is unknown and the best answer is that the tendency to develop psoriasis is part of an affected person’s constitution and some factor triggers the development of the clinical lesions.
Known factors include physical or emotional stress, local trauma to the skin (Koebner’s phenomenon), infection (in guttate psoriasis), drugs (beta blockers, lithium, and antimalarial drugs). Treatment comprises ointments and pastes, systemic drugs, or various forms of ultraviolet light.
The treatment should suit the type of psoriasis.
The age and health of the patient, social and occupational factors need to be taken into consideration.
The motivation of the individual patient is also important.
The preparations mentioned in the text are listed in the formulary in chapter 26. It is estimated that 80% of patients with psoriasis do not consult a doctor, as the lesions are minimal. Local treatment
Local treatments entail the use of ointments and pastes, usually containing tar in various forms.
It is much easier to apply them in hospital than at home if patients can make the time for hospital visits.
Inpatient treatment can be more intensive and closely regulated; it also has the advantage of taking the patient completely away from the stresses of the everyday environment.
In some units a “five day ward” enables patients to return home at weekends, which is particularly important for parents with young children.
Coal tar preparations are safe and effective for the stable plaque-type psoriasis but will irritate acute, inflamed areas.
However, tar may not be strong enough for thicker hyperkeratotic lesions.
Salicylic acid, which helps dissolve keratin, can be used in conjunction with tar for thick plaques.
Refined coal tar extracts can be used for less severe areas of psoriasis.
Ichthammol, prepared from shale rather than coal tar, is less irritating and has a soothing effect on inflamed skin.
It is therefore useful for “unstable” or inflamed psoriasis, when tar would not be tolerated.
Dithranol, obtained originally from the Goa tree in south India, is now made synthetically.
It can easily irritate or burn the skin, so it has to be used carefully and should be kept from contact with normal skin as far as possible. For hospital treatment pastes are used and the lesions surrounded by petroleum jelly to protect the normal skin.
Dithranol creams can be used at home they are applied for 30 minutes and then washed off.
A low concentration (0·1%) is used initially and gradually increased to 1% or 2% as necessary.
All dithranol preparations are irritants and produce a purple-brown staining that clears in time.
If used in the scalp dithranol stains red or fair hair purple.
Emollients soften dry skin and relieve itching.
They are a useful adjunct to tar or dithranol.
Corticosteroid preparations produce an initial clearing of psoriasis, but there is rapid relapse when they are withdrawn and tachyphylaxis (increasing amounts of the drug having a diminishing effect) occurs.
Strong topical steroids should be avoided.
Only weak preparations should be used on the face but moderately potent steroids can be used elsewhere: (a) if there are only a few small lesions of psoriasis; (b) if there is persistent chronic psoriasis of the palms, soles, and scalp (in conjunction with tar paste, which is applied on top of the steroid at night); and (c) in the treatment of psoriasis of the ears, flexures, and genital areas.
In flexural psoriasis secondary infection can occur and steroid preparations combined with antibiotics and antifungal drugs should be used, such as Terra-Cortril with nystatin and Trimovate.
Systemic corticosteroids should not be used, except in life threatening erythroderma, because of the inevitable “rebound” that occurs when the dose is reduced.
The management of psoriasis in patients taking steroids for an unrelated condition may require inpatient or regular outpatient attendances to clear the skin lesions.
Calcipotriol and tacalcitol, vitamin D analogues, are calmodulin inhibitors used topically for mild or moderate plaque psoriasis.
They are non-staining creams that are easy to use but can cause irritation.
Sometimes a plateau effect is seen with the treatment becoming less effective after an initial response.
If so, other agents, such as tar preparations, have to be used as well to clear the lesions completely.
It is important not to exceed the maximum recommended dose so as to prevent changes in calcium metabolism.
Ultraviolet treatment (phototherapy)
Ultraviolet B is short wavelength ultraviolet light and is used for widespread thin lesions or guttate psoriasis.
The dose has to be accurately controlled to give enough radiation to clear the skin without burning. Recently, “narrow waveband” ultraviolet B treatment has been developed, which increases the therapeutic effect and diminishes burning.
It can be used instead of psoralen with ultraviolet A in many cases. Ultraviolet A is long wavelength ultraviolet light, which activates psoralens in the skin.
This results in diminished DNA synthesis and hence reduced epidermal turnover.
The combination of psoralen with ultraviolet A is known as PUVA therapy: a dose of 8-methoxypsoralen (8MOP), 0·6–0·8mg/kg body weight, is taken one to two hours before treatment. 5-Methoxypsoralen is also used, particularly in patients develop itching or nausea with 8MOP.
Other long term cumulative side effects of ultraviolet treatment include premature ageing of the skin, lentigenes, and eventually cutaneous malignancies. For this reason the total cumulative dose is kept below 1000 Joules.
After medical assessment treatment is given two or three times a week, with gradually increasing doses of ultraviolet A.
Once the psoriasis has cleared maintenance treatments can be continued once every two or three weeks. Protective goggles are worn during treatment with ultraviolet A and dark glasses for 24 hours after each treatment.
The glasses are tested for their effectiveness in screening ultraviolet A light.
A variable degree of erythema and itching may occur after treatment. Longer term side effects include a slight risk of epitheliomas developing, premature ageing of the skin, and cataract formation (which can be prevented by wearing ultraviolet A filtering goggles during and after treatment).
The total cumulative dosage is carefully monitored and kept as low as possible to reduce the risk of side effects.
Systemic treatment
Extensive and inflamed psoriasis that is resistant to local treatment may require systemic treatment.
A number of antimetabolite drugs (such as azathioprine and hydroxyurea) and immunosuppressive drugs (such as ciclosporin A) are effective, but the most widely used are methotrexate and acitretin.
Methotrexate inhibits folic acid synthesis during the S phase of mitosis and diminishes epidermal turnover in the lesions of psoriasis.
Because it is hepatotoxic liver function has to be assessed initially and at regular intervals during treatment.
The dosage must be monitored, and when a total of 1·5 g is reached a liver biopsy is indicated to exclude significant liver damage.
Although it is rare, bone marrow suppression can occur insidiously and rapidly in some patients.
In order to detect this an initial test dose is followed by a full blood count.
If this gives normal results a weekly dose of 7·5–15 mg is used.
As it is excreted in the urine, the dose must be reduced if renal function is impaired.
Aspirin and sulphonamides diminish plasma binding.
Methotrexate may interact with barbiturates, paraaminobenzoic acid, phenytoin, probenecid, phenylbutazone, oral contraceptives, and colchicine.
Acitretin is a vitamin A derivative that can be prescribed only in hospital in the United Kingdom.
It is useful in pustular psoriasis and has some effect on other types of psoriasis. However, the effect is increased when combined with PUVA.
Minor side effects include drying of the mucous membranes, crusting in the nose, itching, thinning of the hair, and erythema of the palms and nail folds.
These are usually not severe and settle when treatment stops.
More serious side effects include hepatotoxicity and raised lipid concentrations.
Liver function tests and serum lipid (cholesterol and triglyceride) concentrations have to be carefully monitored.
Etretinate is teratogenic and should only be taken by women during reproductive years if effective contraception is used during treatment and for two years afterwards, as the half life is 70–100 days.
Ciclosporin A is an immunosuppressant widely used following organ transplantation.
It is effective in suppressing the inflammatory types of psoriasis.
Blood tests should be carried out before starting treatment, particularly serum creatinine, urea, and electrolytes, as ciclosporin A can interfere with renal function.
