Immune Deficiencies and Genetic Variations

- Overview

Immune deficiencies are characterized by a compromised ability of the immune system to fight infections, with causes including inherited or spontaneous genetic variations, immunosuppressive drugs, and infections. 

Genetic causes, known as Primary Immunodeficiency Disorders (PIDDs), can result in non-functional immune cells like B or T lymphocytes. 

While most are rare, they typically manifest in early childhood with an unusually high number of infections, and over 40 genetic defects have been identified, with examples including Severe Combined Immunodeficiency (SCID) and X-linked agammaglobulinemia. 

A. Causes of Immune Deficiencies:

1. Genetic Factors:

• Inherited Variations: Mutations in genes that are passed down from parents can cause Primary Immunodeficiency Diseases (PIDs). 
• Spontaneous Mutations: New mutations can occur in the sperm, egg, or fertilized egg, leading to a genetic defect in the affected person, even without a family history. 

2. Environmental and Lifestyle Factors:

• Drugs: Certain medications, such as those used for cancer treatment (chemotherapy) or to prevent organ transplant rejection, can suppress the immune system. 
• Infections: Some infections, like HIV, can damage and weaken the immune system. 

B. Characteristics of Genetic Immune Deficiencies:

• Early Diagnosis: Because the immune system does not function correctly from birth, individuals with PIDDs often experience a higher-than-average number of infections and are typically diagnosed early in life. 
• Susceptibility to Infections: Individuals may be susceptible to infections that are normally harmless to people with healthy immune systems. 
• Symptoms: Signs can include frequent and prolonged infections, chronic infections that are difficult to treat, or infections from unusual pathogens. 

C. Examples of Genetic Deficiencies:

• Severe Combined Immunodeficiency (SCID): A condition where T cell development is affected, leading to a severely compromised immune system.
• X-linked agammaglobulinemia: Results in a lack of B cells, which are crucial for producing antibodies to fight infection.
• Severe Congenital Neutropenia (Kostmann disease): Causes persistently low levels of neutrophils, a type of white blood cell that fights bacterial infections.  

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