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P soriasis is a chronic inflammatory disease of the skin characterised by a relapsing and remitting course. It manifests as pink, scaly, raised lesions on the elbows, knees, lower back and scalp along with certain nail changes like pitting, discolouration, subungual hyperkeratosis and onycholysis in about 25-50% of the cases. In 5-10% of patients, the disease can be associated with joint involvement. 

It is multifactorial in aetiology, with genetic factors and environmental insults playing their role. A positive family history is present in about one third of the patients; when neither parents are affected the risk is about 7.5%, when one parent is affected it is about 15% and when both parents affected, it is 50%. Psoriasis is not contagious.

The following factors may exacerbate the disease:

Psoriasis is not a contagious disease

  • Stress
  • Trauma
  • Infections (Streptococcal upper respiratory tract infections)
  • Medications (Lithium, Antimalarials, Propranolol and other beta blockers, NSAIDS, Terfenadine and steroid withdrawal)
  • Winter season

Role of Diet: Diet has been suggested to play a role in the aetiology and pathogenesis of psoriasis. Diets with low carbohydrates and rich in vegetables and omega 3 polyunsaturated fatty acids (fish such as meckerel, salmons, sardines) improved psoriatic symptoms in some studies.

Animal studies indicate that fatty acids can modulate pro-inflammatory cytokine production and actions. Omega 6 polyunsaturated fatty acids such as arachidonic acid (from meat, refined vegetable oils) enhance interleukin 1 production and tissue responsiveness to cytokines whereas omega 3 polyunsaturated fatty acids such as eicosa pentanoic acid (EPA) and docosa hexanoic acid (DHA) (from fish such as meckerel, salmons, sardines) have the opposite effect. Arachidonic acid is converted to prostaglandin (PG) E2 and leukotreine (LT) B4 which are proinflammatory whereas EPA and DHA are converted into PGE3 and LT B5 which are anti inflammatory. Overproduction of arachidonic acid derived eicosanoids have been implicated in many inflammatory and autoimmune disorders including psoriasis. A diet rich in vegetables and fish is beneficial because it is associated with reduced arachidonic acid intake. Low calorie diet helps in reducing the oxidative stress and thereby improves psoriasis. Weight reduction in obese also helps in improvement of psoriasis.

Age of onset is usually 16-22 years and 57-60 years. The lesions vary from a few to numerous and when numerous, tend to be symmetrically distributed.

At the microscopic level, the skin shows excessive cellular proliferation, poor differentiation and inflammation.

Treatment: Treatment of psoriasis is aimed at reducing cellular proliferation (anti-tumor agents) and inflammation (anti-inflammatory agents) in addition to taking care of the precipitating factors. Treatment is long term with regular follow-up.

Topical:

Avoidance of stress and regular use of emolients prevents exacerbation

  • Emollients - liquid paraffin
  • Keratolytic agents - salicylic acid
  • Coal tar
  • Anthralin
  • Topical corticosteroids
  • Calcipotriene
  • Topical retinoids - Tazorotene

Phototherapy

  • UVB
  • Narrow band UVB

Photochemotherapy

  • PUVA

Systemic

  • Methotrexate
  • Hydroxyurea
  • Azathioprine
  • Retinoids – Etritinate
  • Cyclosporine
  • Sulfasalazine (for arthritis)
  • Biological response modifiers

Guttate Psoriasis

Guttate Psoriasis

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Last Updated: Nov 25, 2006