EDP column by Dr Ketan Dhatariya

“My son has developed scaly areas on his knees and elbows. Our doctor tells us he has psoriasis. What is this?"

Psoriasis is a recurrent non-infectious, inflammatory condition of the skin. It causes raised red patches of skin covered with silvery scales. The skin is made of several layers. The outermost layer is known as the epidermis. Normally this layer is produced by a sheet of cells that divide relatively slowly. These newly formed cells are then gently pushed towards the surface by the new cells being produced underneath. As they rise to the surface, they die and become hard. They eventually get to the surface – the skin you see and feel – before they flake off. So skin is constantly being replaced from beneath. This process usually takes about a month. However in psoriasis, this process takes a little under a week.

About 2% of the population has psoriasis to some degree. It is rare to occur in children under 10, with most people getting it between 15 and 40 years old. It is usually a long term condition that comes and goes. There seems to be a genetic element to the condition, with there being a 1 in 2 chance if both parents have it. 

Because even mild trauma is a common precipitant, he sites most commonly affected are the scalp, the elbows and the knees. But also the parts of the skin that lies next to each other – such as between the buttocks or under the breasts, as well as in the armpits. The nails are also commonly affected.

Treatment consists of several approaches. Soap substitutes such as aqueous cream can be helpful, as well as coal tar preparations. For more stubborn areas, mild to moderate steroid ointments can be used. There are also ointments that reduce the excess proliferation that are derived from vitamin D. Because of the effect of Vitamin D (the vitamin that comes from sunshine) people who have more severe disease may be treated with ultraviolet light treatment.  Often a tablet called psoralen is taken with this treatment to allow more light to be absorbed.

Very occasionally tablets need to be taken to suppress the overactive skin cell proliferation but these need to be taken under strict supervision.

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