The term "primary immunodeficiency diseases" (synonym: immunodeficiency syndromes) covers various diseases of the immune system that are characterized by a temporary or irreversible disturbance of the immune function. Congenital or primary immunodeficiencies (PID) are diseases in which the immunodeficiency is congenital, familial and/or inherited. The PID group is contrasted with diseases in which the immunodeficiency is acquired, which are referred to by the generic term "secondary immunodeficiencies". The best known example of this is AIDS (acquired immune deficiency syndrome).
Immune dysregulation can be a significant indicator for the presence of PID. Associated autoimmune phenomena, e.g. autoimmune-mediated cytopenias or thyroid dysfunctions, are regularly observed in PID. Slow progressive lymphoproliferation, splenomegaly or lymph node swelling or acute phases of hemophagocytic lymphohistiocytosis may thus be an expression of congenital regulatory disorder. Therapy, depending on the clinic, includes wait-and-see approach up to administration of strong immunosuppressive therapy or stem cell transplantation.
Of particular interest is a group of immune dysregulations with susceptibility to EBV. Affected are 10 genes whose mutations cause deficiencies of T cells. The consequence is persistent EBV infections often combined with benign lymphoproliferation and an eminent risk for the development of EBV-associated B-cell lymphoma. Occasionally, photosensitivity(CARMIL2 defect), signs of atopy or SLE-like autoimmunology(PRKCD defect) occur.