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Primary immunodeficiencies (PIDs)


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Primary immunodeficencies (PIDs) are rare diseases in which the immune system is unable to produce the antibodies or cells that are responsible for ensuring the defense against microbial agents present in the environment. This results in a significant reduction in the immune defenses which determines an increased susceptibility to infections often sustained by opportunistic microorganisms, which are normally harmless for a healthy person. Neoplasms, especially of the lymphatic system, autoimmune and allergic diseases are also more frequent in PID patients. The prognosis of PIDs varies according to the type of immunological alteration and the possibility of adequate therapeutic intervention, as well as the severity of the complications associated to the underlying disease.

The most severe congenital forms (severe combined immunodeficiencies or SCID, adenosine deaminase deficiency, sex-linked agammaglobulinemia or Bruton's disease) manifest early in neonatal period or early childhood with severe or repeated bacterial, viral, fungal and protozoal infections. They are identified and treated by pediatricians. Other milder forms such as selective IgA deficiency, certain immunoglobulin sub-class deficiencies or myeloperoxidase deficiency may not significantly compromise defense capabilities and may only be detected during adulthood in patients who have suffered from recurrent infections from childhood while not developing serious clinical pictures. A growing number of genetic defects causing immunodeficiencies with a wide variability of clinical pictures have recently been described. Immunological tests (blood tests) aim at defining the type of defect and the cell subset (T, B, NK) involved. In some cases, these tests are very informative, such as the quantification of immunoglobulins, lymphocyte subsets (immunophenotype) and their functionality in vitro. In other cases, specific tests are required, performed in specialized laboratories. Diagnostic confirmation is possible by performing genetic analysis.

In most cases patients carry an inherited genetic alteration, causing a defect in the development, maturation or function of the immune cells or the lack of a complement system protein in the blood. The latter system is a set of plasma proteins that enhance the innate immune defense. Currently, more than 400 genes have been identified, whose mutations determine the onset of a primary immunodeficiency.

The treatment of primary immunodeficiencies is carried out at several levels. An early diagnosis allows the initiation of prophylactic administration of anti-infective drugs and/or human immunoglobulins with the aim of preventing the onset of infections or their evolution in a serious form, in order to compensate for the defective mechanism by protecting the individual from the aggression of pathogens for which he is vulnerable. Depending on the type of defect identified, it is sometimes also possible to administer enzyme replacement therapies that replace the function of the missing protein by improving the survival and function of the compromised branch of the immune system. These therapies must be maintained constantly and are often not sufficient to guarantee survival in the most severe forms, such as SCID, which can lead to death in the first few years of life if untreated. Currently, for these forms and other primary immunodeficiencies, allogeneic hematopoietic stem cell transplantation is the only potentially curative therapeutic option. At Ospedale San Raffaele, for adenosine deaminase deficiency (ADA SCID) it is possible to perform autologous transplantation of hematopoietic stem cells engineered with the correct gene (gene therapy), approved by the European drug agency and available on the market since 2016 with the name of Strimvelis ™. Experimental gene therapy approaches are being studied for Wiskott-Aldrich syndrome (WAS) in the clinical phase and other forms of primary immunodeficiency in the preclinical phase (CD40L, DADA2, RAG1/2, osteopetrosis.

REFERRING DOCTORS for this desease
at Ospedale San Raffaele

Ospedale San Raffaele - Milano, via Olgettina 60, 20132 Milano, Italia - Tel. 02 26 431
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