Combined immunodeficiency

Combined immunodeficiency (CID) is categorized to the first classification from the international union of immunological societies expert committee for primary immunodeficiency.Severe combined immunodeficiency (SCID) is the most fatal disorder for paediatric clinical operation.Without hematopoietic stem cell transplantation, almost all infants would die before 1 year old, few could survive beyond 2 years old.Hypomorphic mutations in SCID genes can lead to atypical phenotypes.The two special SCID should be focused, Omenn syndrome and graft-versus-host disease, which are caused by expension of autologous and maternal activated and memory T lymphocytes, respectively.Patients with radiosensitive-CID usually present later on life, for whom treatment should be monitored carefully.CID caused by T cells with normal development and inborn error was hotspot research field for example zeta chain-associated protein 70 kDa deficiency.More attention should be paid to CID associated with syndromes for example dedicator of cytokinesis 8 deficiency.Now, the pathogenesis, molecular, clinical, laboratory features and treatment and prognosis are described, in order to support clues for paediatrician′s clinical practice. Key words: Atypical severe combined immunodeficiency; Radiosensitive-combined immunodeficiency; Zeta chain-associated protein of 70 kDa deficiency; Dedicator of cytokinesis 8 deficiency