Severe combined immunodeficiency (SCID) / combined immunodeficiency syndromes

SCID overall incidence is about 1/50,000–1/58,000 live births in high-income settings, with higher frequencies reported in consanguineous or isolated populations. X-linked IL2RG defects account for around 30% of SCID in Western cohorts; other monogenic causes include ADA, JAK3, IL7R, DCLRE1C (Artemis), RAG1/2 and others. Without treatment, most affected infants die from severe infections within the first 1–2 years of life.