Table 2.

Similarities and differences between chronic chikungunya arthritis and rheumatoid arthritis.

	Chronic chikungunya arthritis	Rheumatoid arthritis
Similarities	Presentation: small joint symmetric polyarthritis (most commonly).
	Patients: middle-aged females (most commonly affected demographic).
	Symptoms: fatigue, arthralgias, arthritis, myalgias, and morning stiffness.
	Labs: normochromic anemia; thrombocytosis, and elevated ESR/CRP.
	Radiographic: joint effusions, bone erosions, marrow edema, synovitis, tendinitis, and/or tenosynovitis.
	Serum cytokine profile: ↑ IL-1β, IL-6, IL-17, and TNF (chronic disease)
	Synovial cytokine profile: ↑ IL-1β, IL-6, IL-7, IL-8, IL-10, IL-15, IL-17, GM-CSF, IFN-α, IFN-γ, and TNF (chronic disease)
	Disability: can be moderate-to-severe (chronic disease)
Differences	Presentation: medium and/or large joint asymmetric mono- or oligoarthritis (less commonly).
	Signs and Symptoms: memory and concentration problems and asthenia/depression can be more predominant than in rheumatoid arthritis.	Signs and Symptoms: association with pulmonary (interstitial) disease and/or rheumatoid nodules.
	Serologies: anti-CHIKV IgM and/or IgG antibodies.	Serologies: anti-cyclic citrullinated peptide antibodies (anti-CCP); rheumatoid factor (RF)
	Causative pathogen: chikungunya virus (CHIKV)	Causative pathogen(s): Epstein-Barr virus, cytomegalovirus, human immunodeficiency virus, human T-cell lymphotropic virus type I -, hepatitis C virus, and others (implicated in the pathogenesis)
	Serum cytokine profile: ↑ IL-1Ra, IL-1β, IL-6, IL-7, IL-8, IL-12, IL-15, and IFN-α (during acute arthritis); ↓ CCL5/RANTES (during acute arthritis); ↑ GM-CSF and TNF (during chronic arthritis).
		Serum cytokine profile: ↑ CCL5/RANTES correlates with disease severity.