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What is psoriasis?

Psoriasis is a chronic inflammatory skin disease characterised by red, scaly patches that are most commonly found on the knees, elbows, trunk, and scalp.

It is a genetic disorder with polygenic inheritance, often triggered by various environmental factors, including infection, trauma, or medication.

Who gets psoriasis?

Psoriasis affects 1.5 to 2% of the population worldwide, with an equal effect on men and women. The condition can start at any age from infancy to the eighth decade, although the two peaks of occurrence are between 20 to 30 years old and 50 to 60 years old.

Psoriasis is a chronic condition, meaning that it may come and go throughout life, varying in distribution and severity at different times.

The condition affects all racial groups, and children whose parents both have the disease have a 41% risk of contracting it too. 

What causes psoriasis?

Psoriasis is thought to be an immune system problem that causes the skin to regenerate faster than average. It is a genetic condition with polygenic inheritance, which means that there is not just one gene that predisposes to psoriasis but many.

It has recently been considered a systemic disease because it is closely associated with metabolic syndrome, which includes conditions such as hypertension, diabetes, obesity, hypercholesterolemia, and cardiovascular disease.

In addition, as many as 30% of patients with psoriasis may develop psoriatic arthritis.

Although it isn’t clear as to what causes the immune system to malfunction, the below are environmental factors that could trigger the condition in addition to genetics:

  • Infections such as streptococcal (especially pharyngitis) and HIV
  • Stress
  • Medication such as steroids, lithium, high blood pressure medication, b blockers, and antimalarial medication
  • Heavy alcohol consumption
  • Smoking
  • Obesity
  • Hormonal factors may worsen psoriasis (pregnancy may worsen psoriasis in 50% of women while it may improve in others)
  • Injury to the skin (sunburn, cuts or burns). Psoriasis occurs in the injured skin and is known as the Koebner phenomenon.

What does psoriasis look like? 

Psoriasis’ typical appearance is well-demarcated thick, red plaques (patches) with thick, greasy scales often referred to as candle wax scale. There are variations in appearance depending on the type and location of psoriasis.  

Common signs and symptoms include:

  • Red patches of skin covered with thick, silvery scales
  • Round to oval patches that often merge into larger areas if the psoriasis is widespread
  • Dry, cracked skin that can bleed or itch
  • Thickened, pitted, or ridged nails
  • Swollen and stiff joints
  • Small scaling spots (commonly seen in children)

Psoriasis most commonly affects the lower back, elbows, knees, legs, soles of the feet, scalp, face and palms.

Are there different types of psoriasis? 

There are several types of this skin condition, and at any point in time, different variants of psoriasis can affect the same individual.

  1. Plaque psoriasis
    ‘Vulgaris’ means the ‘common’ and, in this case, most often refers to chronic plaque psoriasis, which accounts for 90% of cases of psoriasis. It usually affects both sides of the body equally, i.e. it is symmetrical in distribution. It can be extensive or minimal, typically involving the scalp, elbows, knees and lower back, and palms and soles.
  2. Guttate psoriasis
    Guttate psoriasis is characterised by small plaques that are widely spread. It typically occurs after an upper respiratory tract infection caused by streptococcus and usually spontaneously regresses after a few months.
  3. Erythrodermic psoriasis
    This is when more than 90% of the skin is affected by psoriasis. It is considered a dermatologic emergency as the person becomes systemically unwell.
  4. Pustular psoriasis
    Pustular psoriasis can occur as a severe complication of chronic plaque psoriasis. It is often precipitated by inappropriate systemic steroid use and withdrawal, pregnancy, hypocalcemia, and infections. The skin is hot and covered with pustules which are just under the scales of psoriasis. The skin is painful, and the patient is feverish and ill. Pustular psoriasis can be localised or generalised. The localised forms affect the hands and feet and present as pustules under the skin.
  5. Inverse psoriasis
    Symptoms of inverse (or flexural) psoriasis include patches of skin that are bright red, smooth, and shiny but don’t have scales. The symptoms get worse with sweating and friction. Inverse psoriasis is usually found in the armpits, groin, under the breasts, or in the skin folds around the genitals and buttocks.
  6. Scalp psoriasis
    The most commonly affected area is the scalp, which may have discrete, individual lesions or merge to cover the entire scalp. The condition is itchy and uncomfortable. The psoriasis is well-demarcated and often extends to beyond the hair margin.
  7. Nail psoriasis
    This condition is characterised by thickening and yellow discolouration of the nail plate. The nail can also separate from the nail bed, becoming tender and painful. Patients with nail psoriasis have an increased incidence of psoriatic arthritis.
  8. Oral psoriasis
    This type of psoriasis is characterised by red rings with a hydrated white scale. It occurs mainly on the tongue in patients with pustular psoriasis.
  9. Psoriatic arthritis
    This condition causes swollen, painful joints that are typical of arthritis. The symptoms can affect any joint and range from mild to severe. Sometimes the joint symptoms are the first (or only) sign of psoriasis.   

Can psoriasis be cured?

Psoriasis is a chronic relapsing condition, which means it may disappear for years at a time on its own. However, there is no actual cure.

Treatments are available to manage the skin to bring about remission or control of the condition.

How is psoriasis treated?

As psoriasis is a chronic disease, a long-term treatment plan is needed. Treatment often changes during the disease’s duration, so a patient can cycle through multiple treatment options in their lifetime.

Treatment depends largely on the extent of the condition and how much it affects the quality of life. The PASI (psoriasis area and severity index) score is used to evaluate this. Comorbidities also affect treatment as they may make some systemic treatments unsuitable.

In general, we try to treat using therapy with the least side-effects. So, when the body’s affected surface area is less than 10%, we will use topical treatments to manage psoriasis.

Systemic medication may be warranted if there are debilitating circumstances affecting occupation or quality of life.

Different types of therapy include the below:

Topical therapy:

  • Coal tar preparations
  • Topical steroids
  • Topical vitamin D derivative in combination with topical steroid
  • Topical calcineurin inhibitors (pimecrolimus, tacrolimus)

Phototherapy

  • UVB light therapy

Systemic Therapy

Traditional therapies:

  • Methotrexate
  • Ciclosporin-a
  • Acitretin

In addition to the above, the below new medications are now available to treat psoriasis:

  • Etanercept
  • Infliximab
  • Adalimumab
  • Ustekinumab
  • Guselkumab
  • Secukinumab

 Below are some general care tips to follow:

  • Keep the skin well-moisturised to alleviate dryness and itching
  • Moisturising softens the scales and aids in preventing fissures and cracks in the skin
  • Don’t pick off scales, as this can lead to bleeding
  • Have warm-water showers (hot water can cause itchiness)
  • Be aware that certain medications can worsen psoriasis.

Although there isn’t a cure for psoriasis, treatment can help relieve the symptoms and manage them. Treatment may vary during the course of the disease and so it’s best to talk to your dermatologist about a long-term plan.