Why do some kids get jra?

Nobody's sure: Jra, juvenile rheumatoid arthritis, was just renamed jia, or juvenile idiopathic arthritis, because the exact cause is unknown. There is some genetic linkage or family history, and a thought regarding certain genetic markers, but mainly it's one of those sporadic autoimmune diseases that affects children seemingly at random.

Most are not JRA!: Jra is an oxymoron, for the most part. Most children have what is now called "juvenile idiopathic arthritis, " which usually are forms of adult spondyloarthropathies in children. My studies (see rheumatology, supplement 1, january 2012, oxford press). Children usually had multiple hla types associated with these diseases, perhaps making them more susceptible. Few are ccp+, a marker for true ra!

Unknown cause: We don't know why some kids get jra(more properly known as jia now) and others don't. We know of many genes that, if you have certain mutations in them, increase the risk for jia but each only increases risk a relatively small amount. What determines whether you get jia also involves some environmental exposure (like common viral infections)at just the wrong time(s) ->immune system gets confused.