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PSORIASIS

Psoriasis is a chronic recurrent dermatosis characterised by sharply demarcated patches and plaques involving the scalp, trunk and extremities. It is a common skin disease which affects about 2% of the population.

 

What is the cause of psoriasis?

 

1.      an immune mediated process with activation / stimulation of  Tlymphocytes

2.      an increase cell turnover with epidermal hyperproliferation

3.      polygenic inheritance with variable penetrance

 

Known triggering factors include the following:

 

1.      streptococcal infection, stress, drugs eg. antihypertensives, antimalarials

2.      trauma

3.      excessive smoking/alcohol consumption

 

What are the clinical presentations of psoriasis?

 

-plaque psoriasis
-pustular psoriasis
-erythrodermic psoriasis ->90% of the skin appears red with scaling.
-guttate psoriasis- occurs commonly in children and is usually preceeded by a
 streptococcal infection.

 

Clinical features

 

-sites of predeliction include the scalp, retroauricular area, knees, elbows, lower back, nails and joints.

What are the treatment options available?

-aim is for combination /rotational/ sequential therapies

 

Topical therapies

 

1.      Tar preparations eg  polytarr shampoo, crude coal tar

2.      Topical steroids –reserved for facial, scalp and flexural psoriasis

3.      Vitamin D analogues eg . Dovonex

4.      Topical keratolytics eg. Salicylic acid

5.      Anthralin derivatives eg Dithranol therapy

6.      Topical retinoids eg. tazorotene (Zorac cream/gel)

 

Light therapy

 

1.      PUVA therapy

2.      Narrowband UVB (TL01 lamps)

3.      Excimer laser –for localised plaque psoriasis

 

Systemic treatment- indicated for severe psoriasis /psoriatic arthritis

 

1.      Methotrexate – works by inhibiting cell turnover and thereby reduces cell    proliferation in psoriasis.

2.      Acitretin  eg  Neotigason

3.      Cyclosporin

4.      Hydroxyurea

 

Biologics

 

1.      These are therapeutic molecules that are specifically targeted in order to imitate or inhibit naturally occurring 

         proteins.

2.      The biologics work by blocking the development of the disease rather than treating the consequences of an    

         abnormal immune function.

3.      These agents have the advantage of being given as a single agent and by injection

 

Infliximab (Remicade)

 

1.      This is a type of biologic that blocks a molecule responsible for the inflammation seen in psoriasis and

         psoriatic arthritis. It is called Tumour necrosis factor (TNF).

2.      This drug blocks TNF from binding with TNF receptor thus neutralising it. It is injected intravenously at

         various time intervals.

 

Etanercept (Enbrel)

 

1.   This biological agent is a TNF receptor blocker. It is a fusion protein and is approved for the treatment of psoriatic arthritis as well as extensive cutaneous psoriasis. It is injected subcutaneously which can be done by patients at home initially twice a week for three months and then less frequently. The onset of action is rapid within 2-3 weeks.

 

Adalumimab (Humira)

 

1.      This is the first TNF alpha blocker that is entirely of human origin. It is also administered by subcutaneous

         injection.