IMMUNODEFICIENCY DISORDERS- Severe combined immunodeficiency (SCID)

IMMUNODEFICIENCY DISORDERS- Primary immunodeficiency diseases (PI)- Severe combined immunodeficiency (SCID)

1. IMMUNODEFICIENCY DISORDERS Severe combined immunodeficiency (SCID) Ms Saajida Sultaana Mahusook

2. IMMUNODEFICIENCY DISORDERS Immunodeficiency disorders prevent the body from fighting against infections and diseases. This disorder makes it easier to catch viruses and bacterial infections. They are either congenital or acquired . Primary immunodeficiencies are genetically determined and can be hereditary; secondary immunodeficiencies are acquired and much more common.

3. Primary immunodeficiency diseases (PI) Primary immunodeficiency diseases (PI) are a group of more than 300 rare, chronic disorders in which a part of the body’s immune system is missing or functions improperly. These diseases are caused by hereditary or genetic defects, and, not contagious . Some disorders are present at birth or in early childhood. It can affect anyone, any age or gender. Some affect a single part of the immune system; others may affect one or more components of the system.

4. Severe combined immunodeficiency (SCID) SCID is a rare, potentially fatal syndrome of diverse genetic causes in which there is combined absence of T-lymphocyte and B-lymphocyte function and occasionally NK cells . Clinically, most patients present before age 3 months. SCID usually results in severe infection and death in children by age 2 years . SCID is considered a pediatric emergency because survival depends on expeditious stem cell reconstitution, usually by bone marrow transplantation (BMT).

5. Bubble Boy Disease SCID is often called “bubble boy disease”. SCID became widely known during the 1970’s and 80’s, when the world learned of David Vetter, a boy with X-linked SCID, who lived for 12 years in a plastic, germ-free bubble.

6. Most common type of SCID is linked to the X-chromosome, making this form affect only males. Other forms of SCID results from mutations in any of more than 15 known genes. These molecular defects interfere with lymphocyte development and function, blocking the differentiation and proliferation of T cells, B cells and NK cells. Antibody production is severely impaired even if mature B cells are present. NK cells, a component of innate immunity, are variably affected. SCID can be detected in a newborn before the onset of infections, with one well-documented example by screening of T-cell–receptor excision circles.  

7. Causes SCID is most commonly due to an X-linked mutation of the gene coding for the γ chain that is common to the receptors for IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21. Deficiency of the Common Gamma Chain of the T-Cell Receptor (X-SCID ) Adenosine Deaminase Deficiency Mutations in Janus Kinase 3 ( JAK3 ) and CD45 Deficiencies of CD3 Chains MHC class II deficiency etc

8. Symptoms Loss of immunity results in severe and opportunistic infections that are more serious and life threatening. It may include pneumonia, meningitis or bloodstream infections.  Children with SCID may develop infections caused by organisms or vaccines, which are usually not harmful to children who have normal immunity.  The following are the more common infections in SCID: Viral infections – Cytomegalovirus (CMV) (pneumonia, hepatitis); enterovirus and rotavirus (diarrhea); Candida albicans  infections – Thrush; diaper dermatitis progressing to diffuse skin involvement; Cutaneous fungal infections Bacterial infections Protozoan infections (diarrhea)

9. Approach consideration Conventional care includes isolation of the patient to avoid infection and meticulous skin and mucosal hygienic care while the patient is awaiting stem cell reconstitution. Parenteral nutrition is customarily provided to children with diarrhea and failure to thrive. Blood product transfusions must be lymphocyte-depleted and irradiated to prevent transfusion-associated graft-versus-host disease (GVHD).

10. Empiric broad-spectrum antibiotics should be administered parenterally during the wait for the results of cultures and body fluid analysis. P rophylactic treatment with nystatin to prevent mucocutaneous candidiasis . SCID is a pediatric emergency and must be addressed expeditiously. Intravenous immunoglobulin ( IVIg ) should be administered promptly. Evaluation for bone marrow transplantation (BMT) should be started. BMT is the primary treatment of choice when an appropriate donor is found. Administration of non irradiated blood products or live-virus vaccines (especially polio or BCG) to a patient suspected of having SCID is an error that may prove dangerous if the patient turns out to have SCID. These children can develop disease from attenuated viruses and may even die after exposure to these vaccines.

11. Reference: https:// primaryimmune.org/about-primary-immunodeficiencies/specific-disease-types/severe-combined-immune-deficiency-and-combined-immune-deficiency http://www.scid.net / https://www.healthline.com/health/immunodeficiency-disorders

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