Psoriasis

Psoriasis is a skin disorder caused by rapid keratinocyte (outer cells of the skin) division leading to a build up cells on the surface the skin and thick red scaly patches. It affects about 1 – 2% of the population and usually begins between the ages of 15 and 30 years. Psoriasis runs a chronic course with periods of exacerbations and remissions. There is no permanent cure but treatment can control the disease and permit a productive life.

Causes

It is not known exactly what causes the rapid keratinocytes cell division but doctors are increasingly viewing psoriasis as an auto-immune disease in which white blood cells known as T-helper cells mistakenly attack the skin cells and cause the release of cytokines (chemicals), including  as tumor necrosis factor (TNF), interleukins (IL), and interferon-gamma which cause inflammation. The newest treatment for psoriasis uses drugs known as biologics to inhibit tumor necrosis factor and one or more interleukins (see treatment). It normally takes a newly formed keratinocyte  about a month to reach the surface of the skin to be sloughed off  but in psoriasis, this is reduced to 3 – 5 days, leading to the build-up of scales. Genetic factors also play a role. A family history of psoriasis can be obtained in 50% of patients with psoriasis and the offspring of a parent with psoriasis has a 1 in 4 chance of developing psoriasis.

Triggers

  • Genetic factors predispose but environmental may trigger the disease and cause it to manifest.
  • Trauma may cause psoriasis to develop in the site of trauma such as along scratches and surgical wounds in a process known as Koebner phenomenon.
  • Infection – Streptococcal sore-throat may trigger guttate psoriasis.
  • Drugs such as beta blockers (used to treat high blood pressure), lithium (used to treat manic-depressive states), antimalarial medicines and non-steroidal anti-Inflammatory drugs (NSAIDs).
  • Alcohol.
  • Smoking.
  • Stress.
  • Stopping systemic steroids.

Symptoms

Plaque psoriasis is the most common type of psoriasis and appears as:

  • Red, inflamed patches of skin covered with thick, silvery scales. The silvery scale comes off easily with scraping to reveal bleeding points, a phenomenon termed the Auspitz sign.
  • Affects any part of the body, especially on the elbows, knees, near the base of the spine and on the scalp.
  • Red glazed patches in the body fold areas such as the armpits and groins.
  • Nail psoriasis is present in 50% of patients and may appear before the skin lesions. It appears as pitted or ridged nails, onycholysis  (detachment from the nail bed) causing a white or salmon pink patch on the nail and subungual hyperkeratosis (accumulation of  scales under the nails due to keratinocyte proliferation). Nail psoriasis is often seen in people with psoriatic arthritis (PsA).
  • Itching may or may not be present.

Psoriasis severity can be graded using the PASI (Psoriasis Area and Severity Index) scale

Other variants:

  • Guttate psoriasis presents as a widespread eruption of small red, scaly spots on the trunk and limbs. Adolescents are most commonly affected and it is often precipitated by a streptococcal sore throat.
  • Palmoplantar pustular psoriasis (PPPP) is characterized by multiple yellowish pustules (pusheads) on the palms and soles. It is more common in smokers.
  • Acropustulosis is characterised by pustules around the nails and the fingertips. It is rare and usually affects young children.
  • Flexural psoriasis (inverse psoriasis) causes well-defined red glazed patches in the body fold areas such as the armpits, groins, natal cleft and beneath the breasts. Scaling is minimal or absent.
  • Napkin psoriasis occurs in children as red macerated or red scaly patches.
  • Acute generalized pustular psoriasis is characterised by red, inflamed, tender skin with sheets of sterile pustules. It develops suddenly over a few hours or days and may be precipitated by stopping systemic steroids. The term von Zumbusch’s pustular psoriasis is used when its accompanied by fever and malaise (feeling of illness). Hospitalisation is usually necessary.
  • Erythrodermic psoriasis is a serious condition with diffuse red inflammation of nearly the entire skin. It may cause hypothermia (lowered body temperature), fever and tachycardia (rapid heart rate). Erythrodermic psoriasis may be triggered by withdrawal of oral steroids, infections, excessive alcohol intake, lithium, and low calcium. Patients usually require hospitalisation.

Complications

  • Erythrodermic psoriasis – A term used for psoriasis that spreads to involve the entire body, causing an erythroderma. It can be triggered by the withdrawal of steroids, infections, excessive alcohol intake, lithium, antimalarial drugs and low calcium.
  • Psoriatic arthritis (PsA) occurs in 25% of patients with psoriasis and can precede skin involvement and present to other specialists. It can affect the small and large joints and even the spine and several patterns of joint involvement have been described. PsA is more common in patients with psoriatic nail disease. Mild arthritis can respond to non-steroidal anti-inflammatory drugs (NSAIDs) but severe arthritis may require strong immunosuppressive drugs and biologics.
  • Psychological morbidity – Psoriasis has an adverse impact on the quality of life as assessed by the psoriasis disability index (PDI). The cosmetic disfigurement, the time required for applying medication and the chronic recurring nature of psoriasis all have an adverse impact on the quality of life and can cause psychological problems, including anxiety and depression.
  • Co-morbidities – Patients with psoriasis have an increased risk of inflammatory bowel disease, coeliac disease, type 2 diabetes), chronic kidney disease, non-alcoholic fatty liver disease (NAFLD), alcohol abuse and the metabolic syndrome which is a constellation of increased blood pressure, excess body fat around the waist, and abnormal cholesterol or triglyceride levels that together increase the risk of heart disease, stroke and type 2 diabetes.

What you can do

  • Avoid scratching as psoriasis tends to develop at sites of skin injury.
  • Apply moisturisers after baths to reduce flakiness and roughness. They help to restore the skins barrier function and relieve itching.  
  • Avoid systemic steroids as they can make psoriasis worse and cause it to become erythrodermic or pustular.
  • Avoid obesity as this may cause psoriasis to develop in the body folds.
  • Sunlight (not sunburn) helps to clear psoriasis.
  • Maintain good physical health by avoiding drug and alcohol abuse, and smoking.
  • Manage stress.
  • Maintain a positive outlook.
  • Learn about psoriasis and consider joining psoriasis support groups.

Treatment

Part of the treatment involves education about psoriasis, identifying and managing co-morbidities and providing psychological support.

Topical treatment

  • Steroids
  • Crude coal tar
  • Dithranol (a tar derivative)
  • Calcipotriol – a vitamin D-like compound
  • Tazarotene (a retinoid).

Phototherapy (light treatment)

  • Ultraviolet B (UVB) – both broadband and narrowband UVB (NBUVB) can be used. Narrowband UVB (NUVB) is safer and more effective.  NUVB can also be combined with tar (Geokerman regime), dithranol (Ingram regime), an oral retinoid called acitretin (Re-NBUVB) or Psoralen ultraviolet A (PUVA) photochemotherapy.  
  • Psoralen ultraviolet A (PUVA) photochemotherapy – involves taking or apply a psoralen prior to shining.  Localised PUVA is also available for targeted treatment to palms and soles.
  • Excimer laser (300nm UVB) for targeted treatment of small areas.

Generally, 2 – 3 treatments per week is required for initial treatment until 75% improvement (usually requires 20 – 30 treatments in total) is obtained then maintenance treatment is begun at a reduced frequency of 1 – 2 times a week for up to 1 year.

Systemic agents

  • Methotrexate (antimetabolite)
  • Acitretin (an oral retinoid)
  • Cyclosporin A (immunosuppressive)
  • Mycophenolate mofetil (MMF) (immunosuppressive)
  • Apremilast (Phosphodiesterase-4 enzyme inhibitor).
  • Biologic agents are the newest treatments for psoriasis. Originally derived from living organisms, they work by blocking pathways that lead to psoriasis. They are effective in treating moderate to severe chronic plaque psoriasis but their high cost limit their wider use. Examples include:
    • Tumour necrosis factor (TNF) inhibitors
      • Etanercept
      • Adalimumab
      • Infliximab
    • Interleukin (IL) inhibitors
      • Secukinumab (IL17A inhibitor)
      • Ustekinumab (IL 12 and IL23 inhibitor)
      • Risankizumab (IL-23A inhibitor)
      • Brodalumab (IL17A inhibitor)
      • Ixekizumab (IL7A inhibitor)
      • Guselkumab (IL23 inhibitor)