Given that allergic/inflammatory symptoms are common in IEI patients and that our patients were all exhibiting remarkably elevated nitrite/nitrate plasma levels compared to controls (27.1 ± 13.8 versus 15.3 ± 5.2 μM, P < 0.05), we chose to investigate the distribution of the polymorphic variants NOS2 −2.5 kb (CCTTT)n and Ser608Leu and NOS3 −786T>C in IEI patients. This evidence concerns the gene NOS2 and inborn error of immunity.