A 46 year-old secretary presents to the primary care office with the chief complaint of a two-month history of left knee pain and swelling as well as diffuse swelling of the right long finger. She says the knee pain and finger swelling is worse in the morning and subsides during the day. She is tired and has been frequently absent from work in the last month.
       The patient’s past medical history is significant for carpal tunnel syndrome of the left hand and she uses a wrist brace for this. Her medical history is also significant for hypertension and migraine headaches. The patient’s medications include Catapres .2 mg once a day. The patient is married, has three children and does not smoke or drink.
       The physical examination reveals a well developed and well nourished woman who is in no apparent distress. Her vital signs include a sitting blood pressure of 136/74, a heart rate of 70 with regular rate and rhythm, and respiration of 16 breaths per minute. She weighs 123 pounds with clothes. She is 5’2” without shoes.
       A physical examination of the skin reveals round, erythematous, plaques with distinct borders and covered with silvery-white, thick scale on the scalp, elbows and knees. Additionally, there is swelling of the left second proximal interphalangeal joint and moderate swelling of the left knee. Diagnostic studies reveal a negative rheumatoid factor and an elevated serum uric acid.

Which of the following is the most likely diagnosis?
A. Reiter’s syndrome
B. Arthritis associated with inflammatory bowel disease
C. Still’s disease
D. Psoriatic arthritis

Key Insights On The Differential Diagnosis
       A. Reiter’s syndrome (reactive arthritis) is not the correct answer. It involves a triad of features: arthritis, conjunctivitis, urethritis or cervicitis. This form of arthritis is most commonly found in young men and develops within days or weeks of either dysenteric or sexually transmitted infection. Chlamydia trachomatis is usually the causative organism of postveneral variety. The dysenteric forms following enteric bacterial infection include: Shigella, Salmonella, Yersinia and Campylobacter. The epidemiology is similar to other reactive arthritis syndromes as it is characterized by sterile inflammation of joints from infections originating at non-articular sites.
       The clinical features of this condition include fever, malaise, anorexia and weight loss. One may also note either buccal ulceration or balanitis. This form of arthritis is most commonly asymmetric and frequently involves large weightbearing joints, usually the knee and ankle. The patient can appear seriously ill and mucocutaneous symptoms can include palanitis, stomatitis, keratoderma and blennorrhagica. Most symptoms disappear within days to weeks. This condition is associated with fever, mucocutaneous lesions, stomatitis, optic neuritis, circinate balanitis, prostates, keratoderma blenorrhagicum (nearly indistinguishable from psoriatic lesions), pericarditis and aortic regurgitation.
       Human leukocyte antigen (HLA)-B27 is positive in 60 to 80 percent of patients. Radiographs include periosteal proliferation, thickening spurs, erosions at articular margins, residual joint destruction, syndesmophytes (spine) and sacroilitis.
       B. Arthritis associated with inflammatory bowel disease is not the correct answer. This is a form of peripheral arthritis. The clinical presentation is spondylitis, asymmetric oligoarthritis that typically involves the knees, ankles and occasionally the upper extremities. Some patients present with ulcerative colitis and the severity of peripheral arthritis findings can parallel bowel disease activity.
       The HLA-B27 antigen is present in most patients in a four to one male to female ratio. Articular features may precede intestinal symptoms and extraarticular manifestations may also occur in Crohn’s disease (erythema nodosum) and ulcerative colitis (pyoderma gangrenosum). Management includes treating the underlying intestinal inflammation with aspirin and using non-steroidal antiinflammatory medications and physical therapy for spondylitis.
       C. Still’s Disease (juvenile rheumatoid arthritis) is not the correct answer. There are three types of juvenile rheumatoid arthritis (JRA): oligoarticular, polyarticular and systemic. The age of onset is less than 16 years with a duration of greater than six weeks.

       Oligoarticular JRA is characterized by fewer than five involved joints and predominately larger joints in the lower extremities. Polyarticular JRA is characterized by more than five involved joints, affects both large and small joints, and rheumatoid nodules are often present. Systemic arthritis is characterized by quotidian fever, which may be accompanied by an evanescent salmon-colored rash and pervasive visceral involvement including hepatosplenomegaly, lymphadenopathy and serositis.
       D. Psoriatic arthritis is the correct answer. Psoriatic arthritis is found equally among men and women. This onset is usually between 30 to 35 years of age and affects approximately 5 to 30 percent of patients with psoriasis. Psoriasis precedes the onset of arthritis in 80 percent of patients while approximately 15 to 20 percent will develop arthritis prior to the onset of skin disease. The arthritis emerges long after or is commensurate with cutaneous psoriasis.
       Forms of psoriatic arthropathy include psoriatic nail disease and distal interphalangeal involvement, asymmetric oligoarthropathy, symmetric polyarthropathy, arthritis mutilans and psoriatic spondylitis. There is an insidious onset and the physical examination is remarkable for peripheral asymmetric arthritis with “sausage” appearance of fingers and toes. Nail changes include pitting, traverse ridging, onycholysis, keratosis, yellowing and nail destruction. Sacroiliac joint involvement is common and psoriatic arthritis may be associated with ankylosing spondylitis.
       Some patients, especially those with spondylitis, will carry the HLA-B27 histocompatibility antigen. Diagnostic studies reveal a negative serum rheumatoid factor, elevated ESR and uric acids. Radiographic findings include osteolysis, distal interphalangeal pencil-in-cup deformity, a lack of osteoporosis, bony ankylosis, asymmetric sacroiliits and atypical syndesmophytes.
Pertinent Treatment Pointers
       When it comes to psoriatic arthritis, clinicians direct treatment at the skin and joints. One should also encourage patients to exercise in order to maintain strength and flexibility. Employing TNF-modulatory agents (etanercept, infliximab) is effective in improving skin and joint disease.
       When treating skin lesions, one may notice an accompanying improvement in peripheral articular symptoms. Nonsteroidal anti-inflammatory medications (eg. Ibuprofen, 800 mgs, three times daily) are effective. Sulfasalazine is reportedly effective in patients with symmetric polyarthrits and intraarticular steroid injections are useful in some settings. Methotrexate and sulfasalazine have clinical efficacy but do not halt joint disease.

Editor’s Note: For a related article, see “What You Should Know About Psoriatic Arthritis” on page 24. Also be sure to check out the archives at www.arthritispractitioner.com.