Psoriasis is not just a skin disease.
In 20% of cases, cutaneous psoriasis is associated with psoriatic arthritis. This can affect the axial joints of the spine and pelvis or the peripheral joints of the knees, feet, hands, etc. One or more joints may be affected. It is an inflammatory rheumatic disease that causes joint pain, especially during the night with stiffness upon waking. There is no relationship between the intensity of skin lesions and the existence of rheumatism. Psoriatic arthritis can also occur in the absence of skin lesions.
Obesity and diabetes are also more common in patients with psoriasis.