Managing Psoriasis in the Tropics

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Introduction

Psoriasis is a common, chronic, inflammatory skin disease of the skin affecting 1-2% of the population all over the world. It is rarely fatal but it is unsightly and may cause anxiety or depression.

Aetiology

Psoriasis is an autoimmune T cell-mediated disease which runs in families. The things that can make it worse are stress, streptococcal infections (sore throat) HIV infection, mechanical trauma (cuts, grazes, operation wounds), drugs such as chloroquine, lithium ß-blockers, and if the patient stops taking systemic steroids or stops using potent topical steroids.

Fig 1 Well defined red scaly plaques on the back Photo: Barbara Leppard

Fig 1 Well defined red scaly plaques on the back
Photo: Barbara Leppard
 

Clinical Presentation

The diagnosis of psoriasis is usually easy. It can begin at any age, but most commonly between the ages of 15 and 30. There are well defined, symmetrical, red, scaly plaques. If you scratch the plaques with your fingernail the scale becomes more obvious. If the lesions are extensive the scale can make a mess in the bed or on the floor.

The scalp and nails are often involved too. In the scalp there are similar red, scaly plaques, but the hair prevents you from seeing them and also stops the scale from falling off. The diagnosis is made by running your hands through the hair. You feel thick scaly lumps. Sometimes the rash extends onto the forehead, the so-called corona psoriatica. The nail changes include pitting (dents on the surface of the nail), onycholysis (the nail lifts off the underlying finger), subungual hyperkeratosis (thick scale under the nail), and orange-brown discolouration underneath the nail.

Fig 2 Scalp psoriasis showing corona psoriatica
Photo: Barbara Leppard
 

Variants of Psoriasis

Guttate Psoriasis
Guttate psoriasis is where there are extensive very small plaques of psoriasis (all the same size, that is, < 1 cm in diameter) which all appear at the same time, 10 - 14 days after a streptococcal throat infection. The lesions last for 2-3 months and then go away. It occurs most frequently in children and young adults. It mostly occurs in people who have never had psoriasis before. Some of them will never have it again, but some will later go on to develop ordinary psoriasis.

Erythrodermic Psoriasis
The whole of the body is involved">More than 90% of the body is red and scaly. This is a dangerous condition in the elderly as it can lead to hypothermia (due to heat loss through the red skin), high output cardiac failure (due to the extensive blood flow through the skin), renal failure (due to fluid loss through the skin) and hypoalbuminaemia (due to protein loss because of the high turnover of cells in the skin). Such patients should be admitted to hospital for monitoring of fluid output and temperature. Treat them with bed rest and lots of moisturisers on the skin. They may need systemic treatment with methotrexate if it does not settle.

Fig 3 Erythrodermic psoriasis. The whole of the body is involved
Photo: Barbara Leppard
 

Generalised Pustular Psoriasis
This is a medical emergency and patients need to be admitted to hospital. Almost the entire skin is red and, more than that, there are recurrent sheets of sterile pustules. The patient feels unwell and may have a fever and rigors. It is usually caused by the patient being given systemic steroids or a potent topical steroid, and then the treatment has been stopped.

Fig 4 Generalised pustular psoriasis
Photo: Barbara Leppard
 

Psoriasis in Patients with HIV/AIDS
Psoriasis may appear for the first time in association with HIV infection, or it may worsen considerably in someone who already has psoriasis. It may develop at any stage of HIV infection, but usually disappears in the terminal stages of AIDS. Any pattern of psoriasis can occur but often there are very hyperkeratotic lesions. Erythrodermic psoriasis and generalised pustular psoriasis can also occur and may be difficult to manage. Psoriatic arthritis is much more common, affecting 20-50% of patients. It is often severe and painful giving a clinical picture similar to Reiter's syndrome and reactive arthritis.

Fig 5 Hyperkeratotic psoriasis on the arm in a patient with HIV infection
Photo: Barbara Leppard

Fig 6 Hyperkeratotic psoriasis on the foot and lower leg in a patient with HIV infection
Photo: Barbara Leppard
 

Fig 7 Psoriatic arthritis in a patient with HIV infection
Photo: Barbara Leppard
 

Treatments

  1. There is no cure for psoriasis. Treatment often works well in removing the scaling and even makes the plaques go away, but it may come back when the treatment is stopped.
  2. Explain to the patient that psoriasis is not contagious and will not harm their general health.
  3. Moisturisers, e.g., petroleum jelly (Vaseline), or Vaseline mixed 50:50 with liquid paraffin, applied twice daily. For many patients this will keep the skin soft and reduce the scaling. This is the only topical treatment that is safe to use in patients with erythrodermic psoriasis or generalised pustular psoriasis.
  4. Sunlight is usually very helpful and is free. Tell the patient to expose the skin affected by psoriasis to the sun for half an hour a day
  5. Topical coal tar ointment works well on the body and on the scalp, but it is messy to use. Collect tar from the nearest road works and mix it with petroleum jelly (Vaseline), making a 3% or 5% ointment (3% is 3gm tar in 97gm Vaseline; 5% is 5gm tar in 95gm Vaseline). Apply either in the morning or at night, whichever is most convenient for the patient. Doing this and exposing the skin to the sun for half an hour/day works even better.
  6. Vitamin D analogues such as calcipotriol, calcitriol, tacalcitrol? and calcineurin inhibitors (tacrolimus, pimecrolimus) are much less messy than coal tar ointments but are very expensive. If available, they are applied twice daily.
  7. Salicylic acid ointment 3-5%, applied twice a day can be useful for removing scale.
  8. Topical corticosteroids should be avoided, if possible, but in many countries are the only form of treatment available. They have a rapid onset of action but their effectiveness diminishes with continued use and increasing amounts are required to give the same effect (tachyphylaxis). When discontinued, the condition may recur with increased severity. Topical corticosteroids in combination with other topical agents, such as tar, vitamin D analogues or salicylic acid, increases their efficacy and reduces the potential for any adverse effects, including the risk of skin atrophy with long term use.
  9. Methotrexate orally or by intramuscular injection. It should only be used in patients with severe disease, or those with moderate disease who have failed other treatments, and/or are very distressed by their extent of disease. It is given once a week only. Give a test dose of 5mng (2.5mg in the elderly and those with poor renal function), either orally or by intramuscular injection. Each week gradually increase the dose of methotrexate until you get to the dose that clears the skin. Do not go above 25mg/week.

Side effects of methotrexate

It is teratogenic so should not be given to pregnant women, or women who might get pregnant.
Bone marrow toxicity. Check a full blood count before starting treatment, then once a week for a month and then every 2-3 months. If the Hb, WBC or platelet count fall below the normal level, stop treatment until it recovers. If the MCV is > 100, reduce the dose.
Fibrosis of the liver. Methotrexate should not be given to patients who drink alcohol or who have had hepatitis in the past. Check the liver enzymes at the same time as the full blood count.
General malaise. It is common for the patient to feel generally unwell for 24-48 hours after a dose of methotrexate.
Nausea, vomiting, diarrhoea and abdominal discomfort.
Stomatitis and uIceration of the mouth.
Most side effects can be prevented by giving 5mg folic acid orally once a week, on a different day to the methotrexate. It seems to be quite safe to give methotrexate to patients with HIV/AIDS.
10. Systemic alternatives to methotrexate are cyclosporin (2.55mg/ kg/day) or acetretin (l0-75mg daily). These are much more expensive than methotrexate and have numerous side effects. If the patient needs these drugs they should only be given by a doctor who is familiar with them.

Mahreen Ameen MA MSc MD MRCP
Locum Consultant Dermatologist
Royal Free Hospital
London NW3 2QG
United Kingdom

Beatrice Etemesi MMed
Consultant Dermatologist
Nakuru
Kenya

Further Reading
1. Ashton R., Leppard B. Differential Diagnosis in Dermatology, 2005. Radcliffe Medical Press.
2. Lebwohl M., Ali S. Treatment of Psoriasis. Part 1. Topical Therapy and Phototherapy.] Am Acad Dermatol 2001; 45: 487-498.
3. Leppard B. An Atlas ofAfrican Dermatology, 2002. Radcliffe Medical Press.
4. Mason J., Mason A.R., Cork M.J. Topical Preparations for the Treatment of Psoriasis: a systematic review. Br ] Dermatol 2002; 146: 351-364.
5. Smith C.H., Barker J.N.W.N. Psoriasis and its management. BM] 2006; 333: 380-384.

Article reference
Ameen M, Etemesi B. Managing Psoriasis in the Tropics. Community Dermatology 2009; Isue No 9. pg 5 - 7 International Foundation for Dermatology

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