isn't it auto-immune?
And yes, the huge money are being made on these "treatments": from Dead Sea salt to weird ointments and strontium injections. Big business, bigger that shaft enlargement products.
However...
There's ancient chinese formula for treating outbreaks of psoriasis - it does not cure it, but certainly makes outbreaks less disturbing and painful. Herbal, cheaper and available in Bangkok China Town pharmacies.
And no, there's no cure. Yet.