Chikungunya Chronic Arthralgia

Chikungunya is an alphavirus (family Togaviridae) transmitted by Aedes mosquitoes (A. aegypti, A. albopictus), with major epidemics in tropical/subtropical regions including the Indian Ocean (2005-2006 La Réunion outbreak affecting 35% of population), Caribbean (2013), Americas (>1 million cases since 2014), and Africa. Acute infection presents with sudden high fever, severe symmetric polyarthralgia/polyarthritis (hallmark, the name 'chikungunya' means 'to walk bent over'), maculopapular rash, headache, myalgia, and lymphadenopathy lasting 7-10 days.

Chronic Chikungunya rheumatic disease develops in 40-60% of patients (some series up to 80%) after acute infection, with symptoms persisting >3 months. Risk factors for chronification include female sex (3:1), age >40 years, severe acute joint involvement, pre-existing joint disease, and high acute viremia. Pathogenesis involves persistent viral RNA detection in synovial cells (months after acute infection), molecular mimicry with self-antigens, chronic synovial inflammation, autoantibody production (RF, anti-CCP positive in 10-20%), and bone erosion (mimicking RA radiographically).

Clinical manifestations include symmetric polyarthralgia (hands, wrists, ankles, knees, feet), morning stiffness, joint swelling, tenosynovitis, fatigue, and depression. Differential diagnosis includes rheumatoid arthritis, post-viral arthritis (parvovirus B19, hepatitis B/C), reactive arthritis, and lupus. Diagnosis based on epidemiologic exposure, acute Chikungunya RT-PCR or IgM serology, persistent symptoms >12 weeks, and exclusion of other rheumatic diseases. ACR/EULAR criteria for RA may be met but anti-CCP usually negative.