Severe combined immunodeficiency: the time for newborn screening has come

Primary immunodeficiencies (PIDs) are a set of about 350 genetic disorders that affect the normal function of the immune system. Advances in genetic diagnosis have allowed the description of new defects in the immune system, broadening the clinical spectrum of PIDs' manifestations beyond susceptibility to infection. Although most PIDs present with recurrent or opportunistic infections, a subgroup of them may be recognized by the early development of auto-inflammatory events, tumors and, paradoxically, the coexistence of autoimmunity and immunodeficiency in the same patient. As their clinical manifestations, the severity of PIDs is highly variable. Severe combined immunodeficiency (SCID), a PID that affects cellular and humoral immunity, is one of the most severe forms of PIDs and the only available curative treatment in Latin America is hematopoietic stem cells transplantation. All patients affected by SCID die during the first two years of life if they are not diagnosed and treated opportunely. In contrast, early transplantation of patients with SCID can lead to excellent survival outcomes. Despite recent advances in the diagnosis of PIDs in Chile, diagnostic resources are not available throughout the country, making the early diagnosis of SCID and other forms of PID difficult in big areas of Chile. The objective of this article is to review general concepts on the pathophysiology, diagnosis, and initial management of SCID and raise the need for the implementation of neonatal screening for SCID in Chile.