Doctors don't know why this happens. Psoriasis may be inherited. You are more likely to have psoriasis if members of your family have it. The symptoms are rough, dry, thick areas of skin. The skin usually does not itch.
Most psoriasis occurs in patches.
Sometimes, however, it appears as many small, droplike, scaly areas. This is called guttate or raindrop psoriasis. Psoriasis can affect your fingernails and toenails, causing them to have pits or dents in them. In severe cases the nails become thick and misshapen. A few people also have arthritis or joint pain with psoriasis.