What can cause a recurrent red pimple like rash on the but checks on a child? she has jra and rash been on and off a while does not itch no fever

Cannot diagnose: This needs to be seen and examined by a doctor for diagnosis, but jra may well produce lesions of this nature. See your pediatrician.

ALL rashes....: ....To be properly diagnosed and treated, have to be seen by a doctor. There are lots of things that can cause a rash like you describe, and what to do about it, if anything, is determined by what's causing it.