MRAP and arthritic joint disease: Enthesitis-related arthritis (ERA), one of the 7 subtypes classified according to the International League of Associations for Rheumatology (ILAR), can be classified by having arthritis and enthesitis or arthritis/enthesitis along with at least 2 of the following: sacroiliitis or inflammatory back pain, positive blood test for human leukocyte antigen (HLA)-B27, arthritis in males with onset age greater than 6 years, symptomatic anterior uveitis, and/or first-degree relative family history of HLA-B27-associated disease [1].