23% of people with psoriasis, that is 28 million the world over, go on to develop psoriatic arthritis. In the US alone there are 1 million psoriatic arthritis sufferers.
It causes pain and inflammation in and around the joints. It is classified as a sero-negative group of joint diseases where the Rheumatoid Factor, seen in rheumatoid joint disease, is negative.
Causes of Psoriatic Arthritis
The exact cause of psoriatic arthritis is unknown, but it is believed to be an autoimmune disease with genetic components. An increased incidence of HLA-CW6, B13, B17 and DR3 have been found in Psoriatic arthritis involving the peripheral joints, while HLA-B27 is raised in psoriatic arthritis with spinal involvement. These are specific gene loci associated with psoriatic arthritis.
Environmental factors also influence the development of psoriasis joint inflammation. Psoriatic arthritis prevalence has been found high in HIV and hepatitis C infections. Antibodies to streptococcal and enterobacterial antigens have also been demonstrated in psoriasis arthritis. Trauma as a precipitating event of the psoriasis joint disease has also been noted.
Clinical Features of Psoriatic Arthritis
Psoriatic arthritis usually has an onset between 40 to 60 years of age, and is preceded by skin lesions in 60-70% cases. Studies show that the skin lesions precede the arthritis by 10-20 years. In 15- 20 % cases, however, the arthritis may appear before the skin eruptions. In 15-20% cases skin and joint involvement occur almost simultaneously. This indicates poor prognosis.
About 95 percent of people with psoriatic arthritis have swelling in joints outside the spine, and more than 80 percent of people with psoriatic arthritis experience changes in their nails such as indentations or lifting of the nail.
Associated symptoms of Psoriatic Arthritis
- Stiffness, pain, swelling and tenderness of the joints and the soft tissue around them.
- Restricted joint movements.
- Stiffness of joints in the morning, called morning stiffness.
- In severe cases there is a sausage like appearance of the fingers and toes.
- The typical psoriasis skin lesions with silvery white scales.
- Psoriasis of Nails: 90% of cases of psoriatic arthritis show pitting, ridges and yellowish discoloration.
- Redness and pain of the eye, similar to conjunctivitis, is another. associated feature of psoriatic arthritis in 30% of cases (Conjunctivitis, Keratitis).
- Kidney involvement, causing hematuria and proteinuria (IgA nephropathy).
- Mitral valve prolapse has been reported in a few cases of psoriatic arthritis, though the association is unclear.
Psoriatic Arthritis: Diagnosis
Psoriatic arthritis can develop at any time. Usually, it appears about 10 years after the first appearance of the skin lesions associated with psoriatic arthritis. The disease can be difficult to diagnose, particularly in its milder forms and earlier stages.
Typically, diagnosis of psoriatic arthritis is based on the patient’s medical history, physical exam, disabling disease if left untreated. In fact, half of those with psoriatic arthritis already have joint and bone damage by the time the disease is diagnosed.
There are some radiological features that are diagnostic of psoriatic arthritis which helps doctors to differentiate psoriatic arthritis from other types of joint inflammation.
Next: Types of Psoriatic Arthritis
