Psoriatic arthritis is a type of joint disease that affects about 30% of psoriasis patients. Usually the skin disease psoriasis, characterized by red skin patches with fine scales, develops first followed by psoriatic arthritis. However, in some patients arthritis may first arise before the skin lesions of psoriasis develops.
Common symptoms include pain, swelling and stiffness of the joints. Usually the joints of the fingers and toes are commonly affected. In severe cases there may be deformities. There is no cure available for psoriatic arthritis but available drugs can control the underlying inflammatory reaction so that symptoms are relieved and disabilities can be prevented.
Psoriatic arthritis and the psoriasis are both chronic diseases. There are alternating periods of remission and attacks. The symptoms often simulate those of other inflammatory joint diseases like osteoarthritis and rheumatoid arthritis. Common symptoms of psoriatic arthritis includes :
- Swollen finger and toe joints with increased stiffness.
- Painful, difficult walking due to pain at the back of the heel and sole.
- Low back pain.
- Nails become separated from the nail bed and may show pitting appearance.
Some patients with psoriatic arthritis may develop arthritis mutilans. This is a condition characterized by destruction of small bones of the fingers leading to severe pain, inability to use the joints and permanent disability.
The exact cause of psoriatic arthritis is not known. However, the immune system which produces antibodies against foreign proteins mistakenly starts producing antibodies against the body’s own tissues (self proteins) and thereby induces the inflammatory response. Certain environmental factors like physical injury or viral and bacterial infections may induce the immune system dysfunction in a genetically susceptible.
There are five different types of psoriatic arthritis depending upon the joint involvement. These are
- Asymmetric. This is the most common type and occurs in about 70% of the psoriatic arthritis patients. This type usually involves less than 3 joints in the body and does not affect the same joint on both sides of the body.
- Symmetric. About 25% of patients suffer from this variety. Joints on both the sides of the body are affected simultaneously. This is the most debilitating form of psoriatic arthritis.
- Arthritis mutilans. Only 5% of patients suffer from this type of severe and destructive psoriatic arthritis. This type of arthritis slowly progresses over years.
- Spondylitis. In this type, it is usually the joints of the neck and back that become stiff but those of the hands and feet may also be affected.
- Distal interpharyngeal predominant is a variety where the terminal joints of the fingers and toes are affected.
- Suffering from psoriasis is the most important risk factor. Usually patients with psoriatic nail lesions are more at risk of developing the arthritic changes.
- Family history of psoriatic arthritis. There are number of known genetic association of which HLA-B27 is one of the most common associations.
- Anyone can be affected with psoriatic arthritis but commonly patients with psoriasis between 30 to 50 years are at more risk.
To date, a definitive cure for psoriatic arthritis is not available. However, drugs are available to control inflammatory reaction to relieve the symptoms and prevent disability. Commonly prescribed drugs include :
- NSAIDs to reduce pain, swelling and stiffness of the affected joints.
- Immunosuppressant agents like azathioprine and cyclosporine.
- Disease-modifying antirheumatic agents.
- TNF-alpha blockers.