Psoriasis is a chronic inflammatory disease of the skin with a relapsing and remitting course. It is relatively common in some ethnic groups, ranging from mild disease in some to severe and debilitating in others, and is a type of skin disease that can severely affect a person`s quality of life.
Psoriasis affects 1-2 % of the population worldwide and afflicts males and females equally. It can occur at any age from infancy to beyond the eighth decade of life but is commonest to begin in the age groups of 20-30 and 40-50. Once it commences, the disease has a chronic course with periods of remissions and relapses.
Psoriasis has a strong genetic predisposition and is associated with certain HLA genes. The chances of inheriting psoriasis if one of your parents has the disease are 14%. If both parents have psoriasis, the chance of each child developing it is 41%.
Inflammation of the skin occurs secondary to a T lymphocyte-mediated immune response. An increased mitotic rate of keratinocytes leads to hyperkeratinization (thickening of the skin).
Various environmental factors can aggravate pre-existing psoriasis or even be the initiating trigger that starts the process in a genetically predisposed individual. These factors may include:
Psoriasis typically presents with classic lesions of well-circumscribed erythematous or salmon pink plaques. They have a characteristic thick and silvery-white scale that overlies these plaques. Peeling away a scale leaves pinpoint areas of bleeding underneath. This particular phenomenon is called the Auspitz sign.
Psoriasis can involve any area of the skin surface but the classic sites of involvement include the scalp, elbows, knees, lower back and periumbilical area. The palms and soles may also be involved.
In psoriasis, the nails may also show signs of the disease. Characteristic nail changes include:
Pitting
Onycholysis
Subungual hyperkeratosis
Oil-drop sign
The disease may manifest in different ways on the skin. The classic distribution is that described for plaque psoriasis but other distribution patterns may occur. These include the following:
-classic areas affected include extensors (knees and elbows particularly) lumbosacral area, scalp, periumbilical area
-may involve other sites in addition
-the face is usually spared
-most common in children and young adults
-acute form usually follows a streptococcal (bacterial) infection
-small round to oval lesions favouring the trunk
-involves flexural areas including groins, perineum, axillae, inframammary
-hyperkeratotic lesions
-more common in HIV-positive patients
-more than or equal to 90% of the body surface area is involved
-may be localized or generalized
-sterile pustules arise on an erythematous base or on pre-existing psoriatic plaques
-may be precipitated by withdrawal from systemic steroids
-can be hyperkeratotic or pustular
– joints may be involved in different patterns
Whilst psoriasis is primarily a disease of the skin, it may be associated with other conditions that involve other organ systems. Some of these diseases may be life-threatening and it is, therefore, necessary to be aware of these associations and actively screen for them in all psoriasis patients. Some of these diseases include psoriatic arthritis, HIV and metabolic syndrome (central obesity, hypertension, Diabetes Mellitus and hypercholesterolaemia).
Because the disease is a chronic one, patients may need to be on some form of treatment or other for many years, if not lifelong. Patients may achieve periods of remissions for many months to years, but there is always a chance that lesions may recur when triggered. Treatment is divided into general measures and specific management options. General measures aim to modify certain lifestyle behaviours and prevent triggers that may aggravate the disease.
General measures
Specific treatments target the actual lesions of psoriasis themselves. This is divided into topical, local and systemic options. Topical treatments are in the form of ointments, creams and lotions applied to the individual lesions. Many different options and formulations are available on the market. These can include:
Phototherapy is a local treatment that incorporates the use of anti-inflammatory ultraviolet light to treat the lesions. Options include narrowband UVB and PUVA.
Systemic treatment may be in the form of immunosuppressive/ immunomodulatory agents or retinoids (derivatives of Vitamin A). These carry the risk of potentially severe side effects; they, therefore, need to be initiated and monitored very carefully. Some systemic treatments that are commonly used include:
Psoriasis is a chronic, sometimes debilitating, disease of the skin that can negatively impact a patient’s quality of life. Treatment options are available but sometimes may be complicated by side effects or other co-morbid conditions that the patient may have. Management under the close observation of a dermatologist is essential.