Psoriasis

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Psoriasis is a recurring, non-contagious skin disorder that is characterised by raised, thickened patches of red skin covered with silvery white scales.


Cause


Psoriasis originates in the immune system.  The key immune system trigger is the activation of T-cells, a type of white blood cell.  Once activated, these cells release cytokines, which are the chemicals used by the immune system to communicate messages.  In psoriasis, these cytokines tell skin cells to multiply and mature at an accelerated  rate, resulting in thickening of the skin.  The redness results from the increased blood supply required for the increased growth of cells.


Aggravating factors


Psoriasis is worsened by stress, alcohol and certain medications 


Types of Psoriasis


  1. •Plaque Psoriasis 

        common type in which there are large patches of red skin with silvery-white scales.

  1. •Guttate Psoriasis 

        small patches, usually less than 1cm in diameter.

  1. •Inverse Psoriasis 

        Psoriasis occuring in the body folds such as armpits and groins

  1. •Eyrthrodermic Psoriasis

        almost the entire body is red with Psoriasis

  1. •Pustular Psoriasis

        small pustules (pus filled areas) are scattered throughout the body

  1. •Nail Psoriasis

  2. •Psoriatic Arthritis


Sites of Psoriasis


Common areas of involvement include:

elbows
knees
scalp
ears
genitalia
nails

flexures - armpits, groins and gluteal cleft (groove between buttocks).  Type of psoriasis where the flexures are predominantly involved is called flexural psoriasis.


typical pitting of the nails in psoriasis


Treatment:


  1. Topical (Applied on the skin)


  1. •2% Ung acid sal
    this medication peels the thickened skin and restores normal skin thickness

  2. •Tar 
    reduces the rapid growth of skin cells

  3. •Dithranol 

  4. •Calcipotriol (Dovonex) 
    effective in restoring normality in psoriasis areas

  5. •Tazarotene (Zorak) 
    a vitamin A derived product with potent effect on psoriasis.


  1. Oral treatments


  1. •Methotrexate

  2. •Acitretin (Neotigason)

  3. •Hydroxyurea

  4. •Cyclosporin

  5. Ultraviolet light


PUVA

narrow band UVB


New treatments for Psoriasis (Biologics)


The biologics are a new line of psoriasis treatments which target specific parts of the immune system.  They therefore are expected to have fewer side effects than existing treatments.  Unlike other systemic drugs, the biologics are administered by injection.


  1. 1. Etanercept (Enbrel)


This biologic has been approved for the treatment of psoriatic arthritis and is undergoing final testing in patients with skin psoriasis.  Intitial studies have shown that half the patients achieved more than 70% clearance and that 70% of patients achieved 50% clearance.  It is administered by subcutaneous injection twice weekly.  Patients can be taught to administer the treatment at home, much like injecting insulin at home for diabetes.


  1. 2. Infliximab (Revellex)


Infliximab is given intravenously in the doctors office.  Initial treatment is administered at weeks 0,2 and 6.  Thereafter, treatment is given at 8 week intervals. 


  1. 3. Alefacept (Amevive


Alefacept is given by intra-venous injection over a 12 week period.  In ne study, more than 30 % of patients saw a greater than 75% improvement of their psoriasis.  Furthermore, improvement has been shown to last for up to 8 months or longer.  Alefacept was the first biologic to be approved by the American FDA.


  1. 4. Efalizumab (Raptiva)


This drug has just been withdrawn from the market because of a rare neurological side effect.


These biologics are at present prohibitively expensive, costing in the range of $1000-00 per month in USA. 


  1. 5. Adalimumab

Self injected subcutaneously


  1. 6. Ustekinumab


Undergoing final clinical tests before registration in SA


The Psoriasis Advisory Board has just put together a set of guidelines for the management of Psoriasis.  This has recently been published in the SAMJ.


To read more about the above treatments, go to
Psoriasis (National Psoriasis Foundation USA)