Palindromic Rheumatism was originally thought to be a variation or the beginnings of Rheumatoid Arthritis, but around 1941 was described and identified by Hench and Rosenberg as a separate disease. Thus, PR used to commonly be referred to as Hench-Rosenberg syndrome. Hench and Rosenberg did coin the name Palindromic Rheumatism, which later became the common name.
In the early years and even now, there's still debate over its separation from RA. While most medical organizations seem to separate the two, the many similarities between the conditions leave some researchers and physicians lumping the two diseases together.