IL5 and rheumatoid arthritis: While relatively low, the implied annual incidence of 20 cases per 10 000 patients is several fold higher than the annual incidence of RA in the UK (1.5 per 10 000 men and 3.6 per 10 000 women).10 Given the wide CIs, however, no firm conclusions can be offered in relationship to our single case and to the relative risk of RA following anti-IL-5 therapy.