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.