Chikungunya viral arthritis in the United States: a mimic of seronegative rheumatoid arthritis.

OBJECTIVE: Chikungunya virus (CHIKV) is an arthritogenic mosquito-transmitted alphavirus that spread to the Caribbean in 2013 and to the US in 2014. CHIKV-infected patients develop inflammatory arthritis that can persist for months or years, but little is known about the rheumatologic and immunologic features of CHIKV-related arthritis in humans, particularly as compared to rheumatoid arthritis (RA). The purpose of this study was to describe these features in a group of 10 American travelers who were nearly simultaneously infected while visiting Haiti in June 2014. METHODS: Patient history was obtained and physical examination and laboratory tests were performed. All patients with CHIKV-related arthritis had detectable levels of anti-CHIKV IgG. Using cytometry by time-of-flight (CyTOF), we analyzed peripheral blood mononuclear cells in CHIKV-infected patients, healthy controls, and patients with untreated, active RA. RESULTS: Among 10 CHIKV-infected individuals, 8 developed persistent symmetric polyarthritis that met the American College of Rheumatology/European League Against Rheumatism 2010 criteria for (seronegative) RA. CyTOF analysis revealed that RA and CHIKV-infected patients had greater percentages of activated and effector CD4+ and CD8+ T cells than healthy controls. CONCLUSION: In addition to similar clinical features, patients with CHIKV infection and patients with RA develop very similar peripheral T cell phenotypes. These overlapping clinical and immunologic features highlight a need for rheumatologists to consider CHIKV infection when evaluating patients with new, symmetric polyarthritis.