The weakened immune system of a person with AIDS or some type of autoimmune disorder may put them at risk for psoriasis. Chemotherapy for cancer can leave a patient vulnerable to this condition as well.
Psoriasis can appear in a number of distinctive forms.
Plaque psoriasis is the most common form. It causes dry, red lesions called plaques which are topped with silvery scales. These plaques can be painful or itchy, and can occur anywhere in the body.
Nail psoriasis, as the name suggests, occurs on fingernails and toenails. The nails can become pitted and discolored. They may become loose and come away from the nail beds. In extreme conditions, the nails may crumble.
Psoriatic arthritis can make the nails pitted and discolored. Any or all joints can become painful. Approximately one-third of those with psoriasis may have psoriatic arthritis.
https://www.empowher.com/psoriasis/content/psoriasis-painful-condition-takes-many-forms