Severe combined immunodeficiency: new advances in diagnosis and treatment.

Severe combined immunodeficiency (SCID) is a condition characterized by lack of cellular and humoral immunity. Uniformly fatal before 1968, SCID was first cured by allogeneic bone marrow transplantation (BMT). Despite improvements in BMT, particularly for cases in which there is no matched related donor, difficulties in SCID treatment persist. Because of incomplete reconstitution and transplant-related complications, gene therapy has been pioneered in SCID with success, but also adverse events in the form of leukemic proliferations related to retroviral insertional mutagenesis. Infectious complications are a major limitation to effective treatment. Early diagnosis of SCID in the pre-symptomatic period could be achieved by population-based newborn screening.