HLA studies in fibromyalgia

Objective Fibromyalgia Syndrome [FMS] is a prevalent rheumatic disorder whose etiology and pathogenesis remains largely unknown. Two previous studies have reported familial clustering of FMS cases and patients with history of "rheumatism" and/or arthritis in first degree relatives. Another study showed the association of HLA-D_R4 antigens in FMS patients, a finding not confirmed in subsequent larger studies. The objective of this study was to investigate the possible association of FMS with individual class I [loci A, B and C] and class II [D_R] human leukocyte antigen [HLA] antigens. Methods: HLA-typing was determined in fifty-two FMS patients [49 females; mean age 46.7 years ±8.9]. All FMS patients met the American College of Rheumatology 1990 classification criteria. Patients were compared with a control group of 869 normal individuals. Loci A and B were determined in all the control population, locus C in 832 and locus DR in 344 of those individuals. All loci were studied by National Institutes of Health [NIH] microlymphocytotoxicity technique. Results: Significant positive associations were noted between FMS patients and HLA B₅₈ [RR = 18.0; pc = 0.0004], D_R5 [RR = 3.6; pc = 0.003] and D_R8 [RR = 14.8; pc = 0.001]. No other HLA associations, including D_R4 antigens, were noted in FMS patients. Conclusions: In our study FMS was associated with individual B₅₈, D_R5 and D_R8 HLA antigens. Our findings suggest the possibility of immunogenetic factors in FMS pathogcnesis. However, the difference between our results and those of former studies suggests the heterogeneity among FMS populations and the need for further investigation.