IPEX patients display normal serum BAFF concentrations. Serum BAFF concentrations (picograms per milliliter) in healthy donors (♢, n = 73) and IPEX patients (♦, n = 9) were measured by ELISA. Each diamond represents an individual, and the average is shown with a bar: healthy donors, 1019 ± 35; IPEX patients, 1177 ± 134.