Ankylosing spondylitis in sub-Saharan Africa.

Ankylosing spondylitis (AS) represents a chronic inflammatory bone disease of the axial skeleton that manifests as chronic back pain and progressive stiffness of the spine. It characteristically affects young adults with a peak age of onset between 20-30 years. In contrast to Western Europe and North America, the disease is rare in Sub-Saharan Africa where the majority of the population is HLA-B27 negative. Even in some African populations where HLA-B27 is prevalent (for example, in Gambia and Senegal, where 3-6% of the general population has HLA-B27), the disease is also said to be rare. However, some other genetic markers may be involved in the causation of AS in the HLA-B27 negative population, and when it occurs in this subgroup of patients it has a similar manifestation with HLA-B27 negative white patients and these patients rarely develop anterior uveitis. The clinical presentation of the disease in Africa is generally milder; most affected individuals do not have a family history of AS, the patients are older at onset of the disease, and the majority of them lack extra-articular manifestations such as anterior uveitis compared with the situation in Western Europe and North America. In conclusion, AS in sub-Saharan Africa seems to represent a subgroup of the disease, which may open the window to a greater understanding of the pathophysiology of the condition.