Plaque psoriasis is a chronic autoimmune condition that appears on the skin in patches of thick, red, scaly skin. It can affect anyone and is not contagious. Plaque psoriasis can be a very itchy and sometimes painful condition.It also can be embarrassing and does not always respond to treatment.laque psoriasis is a chronic autoimmune condition that appears on the skin in patches of thick, red, scaly skin. It can affect anyone and is not contagious. Plaque psoriasis can be a very itchy and sometimes painful condition. It also can be embarrassing and does not always respond to treatment.