The mRNA expression of the three BAFF receptors (BAFF-R, TACI, and BCMA) on total B-cells in patients with PAPS revealed no difference with healthy controls, in contrast to patients with SLE, which had higher expression of BCMA and lower expression of BAFF-R and TACI in bulk B-cells. This evidence concerns the gene TNFRSF13B and systemic lupus erythematosus.