A population study on rheumatoid arthritis in Lesotho, southern Africa.

Motivated by the results of a hospital study on rheumatoid arthritis (RA) in Lesotho (southern Africa) a survey of inflammatory polyarthritis (IP) and RA was undertaken in a sample of the rural population of that country. Contrary to expectations the prevalence of IP grades 2-4 (definite disease) was low (0.4%) and equal in both sexes, while probable and definite RA combined (American Rheumatism Association (ARA) criteria) occurred in 1.8% of both males and females. RA was slightly more severe than in other rural African Negro studies but less so when compared with the disease condition of the patients observed in the hospital study. Rheumatoid factor and particularly that directed against heterologous antigen occurred in 41% of the RA patients and in 16% of the controls. Two thirds of the definite cases and 29% of the combined probable and definite group showed radiological abnormalities.