title: Severe combined immunodeficiency--an update.
abstract: Severe combined immunodeficiencies (SCIDs) are a group of inherited disorders responsible for severe dysfunctions of the immune system. These diseases are life-threatening when the diagnosis is made too late; they are the most severe forms of primary immunodeficiency. SCID patients often die during the first two years of life if appropriate treatments to reconstitute their immune system are not undertaken. Conventionally, SCIDs are classified according either to the main pathway affected by the molecular defect or on the basis of the specific immunologic phenotype that reflects the stage where the blockage occurs during the differentiation process. However, during the last few years many new causative gene alterations have been associated with unusual clinical and immunological phenotypes. Many of these novel forms of SCID also show extra-hematopoietic alterations, leading to complex phenotypes characterized by a functional impairment of several organs, which may lead to a considerable delay in the diagnosis. Here we review the biological and clinical features of SCIDs paying particular attention to the most recently identified forms and to their unusual or extra-immunological clinical features.
authors.affiliation: Department of Translational Medical Sciences, Pediatrics Section,  Federico II University, Naples, Italy.
authors.forename: Emilia
authors.initials: E
authors.lastname: Cirillo
authors.affiliation: Department of Translational Medical Sciences, Pediatrics Section,  Federico II University, Naples, Italy.
authors.forename: Giuliana
authors.initials: G
authors.lastname: Giardino
authors.affiliation: Department of Translational Medical Sciences, Pediatrics Section,  Federico II University, Naples, Italy.
authors.forename: Vera
authors.initials: V
authors.lastname: Gallo
authors.affiliation: Department of Translational Medical Sciences, Pediatrics Section,  Federico II University, Naples, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: D'Assante
authors.affiliation: Department of Translational Medical Sciences, Pediatrics Section,  Federico II University, Naples, Italy.
authors.forename: Fiorentino
authors.initials: F
authors.lastname: Grasso
authors.affiliation: Department of Translational Medical Sciences, Pediatrics Section,  Federico II University, Naples, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Romano
authors.affiliation: Department of Translational Medical Sciences, Pediatrics Section,  Federico II University, Naples, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Di Lillo
authors.affiliation: Department of Translational Medical Sciences, Pediatrics Section,  Federico II University, Naples, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Galasso
authors.affiliation: Department of Translational Medical Sciences, Pediatrics Section,  Federico II University, Naples, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Pignata
mesh_terms: D006801:Humans; D016511:Severe Combined Immunodeficiency / Q000145:classification* / Q000175:diagnosis* / Q000453:epidemiology / Q000235:genetics* / Q000276:immunology* / Q000473:pathology
keywords: DiGeorge syndrome; SCID; cytokine; nude/SCID; primary immunodeficiency; severe combined immunodeficiency; thymus