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Immunodeficiencies

• Any defect in the immune response that renders an individual more susceptible to infectious diseases that would be cleared by a healthy person.
• Patients with immunodeficiency diseases are more prone to contracting infections, and these infections are more likely to end in long-term debilitation or death.
• They also have a higher risk for developing autoimmunity or cancer.

Primary Immunodeficiencies

• Mostly inborn (genetic) and often detected in infancy or childhood, though some are detected in adulthood.
• Include B-cell deficiencies, T-cell deficiencies, and innate immunodeficiencies.

B Cell Deficiencies

• Isolated IgA deficiency: 1/600, inability to produce IgA, normal levels of other antibodies and lymphocytes.
• Common variable immunodeficiency: 1/50,000, defects in most classes of antibody secretion, inability of helper T-cells to amplify antibody production, and assorted defects in the innate immune system.
• X-linked agammaglobulinemia (Bruton's): 1/250,000, inability of Pro-B cells to differentiate into Pre-B cells, lack of a tyrosine kinase that initiates recombination and antibody formation.
• Hyper IgM syndrome: 1/1,000,000, patients make IgM but have difficulty producing IgG, IgA, and IgE, inability of helper T-cells to activate B-cells and macrophages.

T-Cell Deficiencies

• DiGeorge syndrome (22q11 deletion): 1-2/2000, T-cell deficiency, thymic hypoplasia, variable loss of T-lymphocytes, increased fungal and viral infections, increased autoimmunity, cardiac abnormalities, craniofacial abnormalities, and developmental delay.

Innate Immunodeficiencies

• Complement deficiencies: 1/20,000, deficits in the complement system, increased risk of infections.
• Hereditary angioedema: 1/50,000, autosomal dominant disorder, deficit in C1 inhibitor, results in unchecked activation of the classical complement pathway, increased bradykinin production, and increased activation of certain components of the clotting cascade.

Infectious Diseases Risk of Systemic Glucocorticoid Use

• Systemic use of glucocorticoids can increase risk of infections.
• Increased risk with higher doses and for greater than 2-4 weeks.
• Examples of specific infections include Pneumocystis jiroveci pneumonia, fungal infection of the lung, and combination antibiotics prophylactically or treatment.

Learn about primary immunodeficiencies, including their definition, pathophysiology, clinical signs, and treatment. This quiz covers B Cell Deficiencies and more.