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 that affects about 2% of the population.
What is the cause of psoriasis?
1. an immune-mediated process with activation/stimulation of Tlymphocytes
2. an increased cell turnover with epidermal hyperproliferation
3. polygenic inheritance with variable penetrance
Known triggering factors include the following:
- streptococcal infection, stress, drugs eg. antihypertensives, antimalarials
- 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 preceded by a streptococcal infection.
Sites of predilection include the scalp, retro auricular area, knees, elbows, lower back, nails, and joints.
What are the treatment options available?
- aim is for combination /rotational/ sequential therapies
- Tar preparations eg polytarr shampoo, crude coal tar
- Topical steroids – reserved for facial, scalp and flexural psoriasis
- Vitamin D analogues eg. Dovonex
- Topical keratolytics eg. Salicylic acid
- Anthralin derivatives eg Dithranol therapy
- Topical retinoids eg. tazorotene (Zorac cream/gel)
- PUVA therapy
- Narrowband UVB (TL01 lamps)
- Excimer laser – for localised plaque psoriasis
Systemic treatment- indicated for severe psoriasis /psoriatic arthritis
- Methotrexate – works by inhibiting cell turnover and thereby reduces cell proliferation in psoriasis.
- Acitretin eg. Neotigason
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
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.
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.
This is the first TNF alpha-blocker that is entirely of human origin. It is also administered by subcutaneous injection.