AS predominantly affects males younger than 40 years. The HLA B27 marker is more common in patients with AS than in the general population. Insidious, chronic lumbar back pain that worsens with rest and improves with activity is characteristic. Patients often complain of pain in their buttocks and upper thighs and may experience soft tissue pain at the bone-tendon junctions. Over time, progressive restriction of spinal motion occurs with prominent kyphosis. Only 10% of patients develop peripheral arthritis however up to 20% may experience iritis which can lead to serious visual complications if untreated.

Young man with ankylosing spondylitis. (courtesy Dr. I. Dwosh)

In 1916, H. Reiter described a cavalry officer with arthritis, urethritis and conjuctivitis following bloody diarrhea ("Reiter's syndrome"). By 1973 a strong association had been made between this disease and a positve HLA B27 antigen. Many patients present with asymmetrical oligoarthritis without eye or GU symptoms. Reactive arthritis is now known to follow certain infectious agents including:

• Chlamydia
• Campylobacter
• Salmonella
• Shigella
• Yersinia
• HIV

A recent history of diarrhea, urethritis, cervicitis, conjunctivitis, uveitis, oral ulceration, or balanitis in combination with new joint complaints is suggestive of reactive arthritis. The Classification Criteria for Reiter's Syndrome are outlined on the ACR webpage.

Conjunctivitis in a patient with Reiter's syndrome. (courtesy Dr. I. Dwosh)

Patients with inflammatory bowel disease (Ulcerative Colitis or Crohn's disease) may develop seronegative arthritis. The bowel symptoms may precede or coincide with joint symptoms. The arthritis may affect large and small joints. Associated symptoms include dactylitis and enthesitis.

Dactylitis (image courtesy of Dr. I. Dwosh)

Psoriasis affects between 3-5% of the population. Between 5-10% of patients with psorasis develop psoriatic arthritis. It is common for skin manifestation to precede joint disease. This is the case in 3/4 of those affected. The arthritis is typically asymmetrical. One third of patients have an oligoarthritis; 40% have a polyarthritis that may mimic RA. Dactylitis and nail changes are commonly seen.

Typical psoriatic skin lesions in patient with arthritis affecting the feet. (courtesy Dr. I. Dwosh)