Severe combined immunodeficiency (familial forms, major monogenic subtypes)

SCID comprises a group of at least 20 monogenic primary immunodeficiencies including familial forms; infants typically present in the first months of life with severe, recurrent and opportunistic infections and failure to thrive, and the disease is uniformly fatal without treatment. X-linked IL2RG-SCID and ADA-SCID are among the more frequent subtypes, but each genetic subtype remains rare.