Abstract
Primary immunodeficiency diseases represent a vast array of inherited disorders of the immune system. Major advances in the understanding of genetic basis and molecular mechanisms have occurred within the past 10 years, as a result of the tools of modern genetics. About three quarters of 100 primary immunodeficiency diseases can now be reliably diagnosed with molecular probes. In many cases, gene identification has enabled significant insight into the physiopathology of the related conditions. Therapeutic progress based on protein engineering and possibly gene therapy will also ensue.