Enthesitis- inflammation at sites of tendinous or ligamentous attachment to bone is another hallmark. It affects men more commonly and usually young adults. It's rare after 40 yrs of age. Most common presentation is LBP, stiffness. Can involve shoulder and hip jts.
Extraskeletal manifestation includes uveitis.
Lab findings include increaed sed rate. HLA-B27 not necessary. Relies on HX, PE schrober's and X-R which shows sacroilitis early on and later bridging syndesmophytes. Characterized by classic triad of uveitis, arthritis and urethritis. Develops post bacterial infection, chlymedia, salmonella, campylobacter, GI tract infection.