Psoriatic arthritis is a form of arthritis associated with psoriasis, a chronic skin disease. Psoriasis is characterized by scaly white and red patches developed on skin. Psoriatic arthritis is caused by an overactive immune system of the body. The joints of knees, toes, wrists, fingers, shoulders and ankles are affected by this disease. It can lead to inflammation, swelling, redness, warmth and pain in joints. Early diagnosis of psoriatic arthritis is essential to start the appropriate treatment. Otherwise, it can cause serious joint damage and deformities.
Physical examination, medical history of the patient, laboratory investigations and imaging tests are important factors for diagnosis of psoriatic arthritis. Physical examination of the patient includes significant changes in skin and nails and joint damage. Medical history of the patient includes information about allergies, previous injuries and other illnesses. Sometimes, skin biopsy is performed to detect the changes in skin due to psoriasis.
After monitoring the symptoms, the doctor prescribes some laboratory tests for confirmation of diagnosis. As symptoms of psoriatic arthritis resemble other forms of arthritis such as gout, rheumatoid arthritis and reactive arthritis, blood tests are performed to rule out other types of arthritis. For example, determination of rheumatoid factor is performed which may help to rule out the possibility of rheumatoid arthritis. Erythrocyte sedimentation rate (ESR) levels may be elevated due to inflammation of the joints in psoriatic arthritis. Determination of serum uric acid is another blood test of which raised levels are suggestive of psoriatic arthritis. Besides this, determination of HLA-B27 is a significant blood test. About 50% of patients having psoriatic arthritis with spine inflammation give positive results for this genetic marker.
When one or two large joints such as knees are involved and inflamed, arthrocentesis is suggested. This procedure involves aspiration of synovial fluid from the inflamed joints through a sterile needle. The joint fluid is analyzed for the presence of uric acid crystals, infection and other inflammatory conditions. Presence of uric acid crystals indicates gouty arthritis. Analysis of synovial fluid is considered as an important step in diagnosis of psoriatic arthritis.
The imaging tests such as x-ray, MRI (Magnetic Resonance Imaging) and CT (Computerized Tomography) scan also useful for the diagnosis of psoriatic arthritis. Common x-ray findings in psoriatic arthritis are changes in cartilage or bone injury which indicates the arthritis of sacroiliac joints, spine and hands. CT scan of pelvis is recommended in case of inflammation of hips, pelvis or spine. MRI scan is performed to detect the involvement of joints, especially feet and hands.
