Testing for association in SLE families.

Systemic lupus erythematosus (SLE) is a complex disease which is partly determined by genetic factors which influence susceptibility to the disease phenotype. In this association study we try to define the high risk haplotypes which are responsible for this disease, together with other environmental factors. In many other association studies a set of SLE patients is compared to a set of controls. The basic assumption about the underlying population is that the disease and control sample should originate from the same genetic population, which is not always completely satisfied in many studies. Therefore, we analyse our family data by applying the Haplotype Frequency Difference (HFD) Method, which constructs its internal control group from those haplotypes not transmitted to the affected individual. Results partially conform with other studies, showing that the haplotypes B8 DR3 as well as B7 DR2 have a high positive association with SLE. When the DR locus was analyzed alone, we found besides the alleles DR2 and DR3 a negative association for DR1, DR5, and DR6.