To determine the aetiological relationship between human T cell leukaemia virus type-I (HTLV-I) and arthritis, by performing an epidemiological study of the inhabitants of Tsushima, an island northwest of the main island of Kyushu, Japan, which is an endemic area of HTLV-I.
A total of 7087 people underwent an annual health check, and those with arthropathy had further physical and radiological examinations by rheumatologists. The presence of HTLV-I antibody was determined by the particle agglutinin method, and integration of the proviral DNA in peripheral lymphocytes was confirmed by polymerase chain reaction.
HTLV-I was positive in 26.1% of inhabitants; the incidence increased to 37.0% in patients with symptoms of polyarthritis. The prevalence of rheumatoid arthritis (RA) was significantly different between HTLV-I carriers (0.56%) and non-carriers (0.31%). The stage of bone destruction in HTLV-I carriers with articular symptoms was milder than that in RA patients without HTLV-I. The relative risk of HTLV-I infection for polyarthritis was 1.66 (p < 0.05).
This is the first epidemiological report clarifying the association between HTLV-I and polyarthritis. Our results suggest that this viral infection has a relationship to RA.