ABSENCE OF RHEUMATOID-ARTHRITIS IN A RURAL NIGERIAN POPULATION

A 2-stage population screening of 2,000 inhabitants of 2 rural townshi ps in southern Nigeria was undertaken. No case of rheumatoid arthritis (RA) was discovered in those responding, although 3 cases of inflamma tory polyarthritis were found. One of these individuals satisfied the modification of the American College of Rheumatology classification tr ee criteria that allows for missing radiographic data. Simultaneous mo nitoring, during a 4-month period, of the local health clinic serving the townships also failed to reveal a case of RA. Three (5.5%) of 55 i ndividuals tested were positive for rheumatoid factor, a rate lower th an in previous surveys of rural West African populations. Further immu nogenetic investigation of that subsample from this population, using HLA oligonucleotide typing, suggested that HLA-DR4 was rare (1155). Fu rther, although HLA-DR1 was present in 7 (13%), 6 had the DRB10102 va riant seen in black populations and not thought to be associated with RA. Our study confirmed the findings of others that rural African grou ps have extremely low rates of RA. In addition HLA genes containing th e RA associated ''shared epitope'' are also relatively infrequent and might explain this reduction in RA prevalence.