Palindromic rheumatism: a descriptive report of seven cases from North Dakota and a short review of literature.

The population of North Dakota is predominantly of Scandinavian (Norwegian) or German descent. We analyzed a cohort of all patients diagnosed with palindromic rheumatism (PR) and followed-up (by the investigator PK) at the St. Alexius Medical Center, Specialty Clinics, Bismarck, North Dakota, from August 16, 2006 to September 16, 2008. Standard statistical methodology was used to analyze the data. The proportion of patients with PR out of the total number of patients with rheumatoid arthritis (RA) seen during the timeframe of this study at our institution was 0.9%. The demographics, clinical features, and response to treatment of our patient-population with PR were quite similar to what has been described in the literature. However, we did not observe an evolution of PR into rheumatoid arthritis or any other "identifiable" inflammatory arthropathy although the follow-up was done very regularly (at least every 3 months), the average duration of follow-up being 12.1 months. Also, testing for the HLA B27 allele was positive in 3 (42.86%) patients, much higher than the "background" prevalence of this gene. This small, longitudinal study describes the epidemiology, clinical features, laboratory and radiographic findings, and course of PR in a small but closed community. This is the first descriptive report of PR to the best of our knowledge from the unique state of North Dakota.