Seronegative rheumatoid arthritis in elderly and polymyalgia rheumatica have similar patterns of HLA association

Objective. To examine whether polymyalgia rheumatica (PMR) and late onset r heumatoid arthritis have identical or similar HLA-DRB1 genetic associations . Methods. Seventy five PMR cases without evidence of giant cell arteritis we re available for study. One hundred seven RA cases were investigated, of wh ich 62 had disease onset after age 60 years. All cases were compared with 1 45 ethnically matched controls. All cases and controls originated From Lugo , NW Spain. HLA-DRB1 typing was performed on DNA samples using PCR based mo lecular methods. Results. Early onset RA (less than or equal to 40 yrs) was strongly associa ted with DRB1*04 (DRB1*0401 and *0404). In contrast late onset RA (greater than or equal to 60 yrs) was not associated with DRB1*04 but was associated with DRB1*01. Stratification of late onset RA cases by rheumatoid factor s tatus revealed that DRB1*01 was only increased in seropositive RA cases. La te onset seronegative RA cases exhibited increased frequency of DRB1*13/*14 , this was also observed in PMR cases where coexistence of GCA bad been exc luded. Conclusion. These data indicate that (1) HLA associations with RA differ wi th respect to age at disease onset: and (2) seronegative late onset RA and "isolated" PMR have a similar HLA-DRB1 association and may have an identica l etiological basis.