Rheumatic diseases in African blacks.

Contrary to previous belief, there is increasing evidence that a broad spectrum of rheumatic diseases do affect African blacks. Although properly conducted epidemiological studies have yet to be performed, reports of population surveys from a variety of sub-Saharan African countries indicate that diseases such as rheumatoid arthritis (RA), gout, and the connective tissue diseases are observed, although some differences in clinical presentation may occur as a result of cultural, racial, and socioeconomic factors. Rheumatoid arthritis is common in some parts of Africa and less common in others. In particular, a significantly lower prevalence of RA in rural areas compared with urban cohorts has led to the hypothesis that environmental factors associated with urbanization may be involved in disease pathogenesis. A similar hypothesis has been suggested for hyperuricemia and gout. Clinical features of disease may also be different in Africans when compared with other population subgroups such as with systemic lupus erythematosus although this may be artefactual as different accessibility to health care and referral practices may result in only the more severe cases coming to medical attention (eg, lupus nephritis). Immunogenetic factors may reduce the prevalence of some conditions such as the spondyloarthropathies. Although the association between HLA-DR4 and RA holds true in Africans, the same is not so for the association of HLA-B27 with ankylosing spondylitis (AS). The prevalence of HLA-B27 in African blacks is 10 times less than Caucasian populations, in part accounting for the low prevalence of spondyloarthropathies, although its association with AS is low. Other conditions such as human immunodeficiency virus (HIV)-related arthropathies appear to be an increasing medical problem. The panepidemic of acquired immunodeficiency syndrome in Africa has resulted in an increased awareness of the different types of arthritis that may be associated with HIV. These are similar to those reported in other parts of the world, although risk factors are different in Africa where heterosexual transmission is a more common cause than homosexual transmission or i.v. drug usage. Information on other rheumatic diseases such as osteoarthritis and soft tissue rheumatism are slowly emerging. Rheumatic manifestations of the infectious diseases, which are endemic in Africa, remain a uniquely fascinating aspect of rheumatology practice on the African continent. Therefore, African countries will increasingly be a continued valuable source of clinical material for comparative studies to help elucidate factors that influence the development of rheumatic diseases.