1. Ankylosing spondylitis
2. Reactive arthritis
3. Psoriatic arthritis
4. Enteropathic arthropathy

Common Features:

1. Men <40
2. involvement of spine and large joints
3. Negative RF
4. Enthesopathy
5. Uveitis
6. HLA-B27

Ankylosing Spondylitis

Reactive Arthritis

Psoriatic Arthropathy

Enteropathic Arthropathy

asso: with UC and Chron's , flares of IBD

sometimes develop characteristic skin lesions: pyoderma gangrenosum and erythema nodosum