Juvenile rheumatoid arthritis.
A form of joint inflammation, occurring in children, in which several of the joints may become inflamed.
Juvenile - in kids
Rheumatoid - means really a form of inflammation with sticky material inside the joint space. In fact this is an old term where the usage is now different from the original meaning. Rheumy - I think used to mean 'mucous-containing'. Correct me if I am wrong.
Arthr - means 'joint'
Itis - means 'inflammation of' - arthritis = inflammation of the joint.
In fact arthritis means more than that these days, but in rheumatoid arthritis the joints do become inflamed - red and hot and painful - usually the small joints mostly (like fingers).
The child is often very ill with it. Fortunately it can 'burn out' with time.