immunodeficiency

Definition: A failure of the body's immune defenses leading to increased likelihood of morbidity or mortality.
Characteristics:
- Can involve deficiencies in cells, proteins, signaling mechanisms.
- Increased susceptibility to infections and potential disruption of homeostatic systems.
- Severity varies widely among individuals.
Types:
- Primary Immunodeficiencies: Genetic origins.
- Secondary Immunodeficiencies: Resulting from other diseases or environmental factors.

Primary Immunodeficiencies:
- Present at birth.
- Inherited through gene mutations that control immune cells.
- Typically observed in children, causing severe recurrent infections.
- Require treatment for recovery.
- Over 150 known types.
Secondary Immunodeficiencies:
- Arise as a consequence of other diseases, aging, malnutrition, or medications.

Role: Help elucidate the genetic underpinnings of immunity.
Severity: Can vary from mild to fatal and are categorized by innate/adaptive immune impacts.
Classification: Based on which immune components are affected (e.g., humoral vs. cell-mediated).

Cell Lineage Impact:
- Myeloid Deficiencies (e.g., chronic granulomatous disease).
- Lymphoid Deficiencies (e.g., Severe Combined Immunodeficiency - SCID).
Key Defects:
- NK cell deficiencies.
- T- and B-cell developmental issues.
- Impaired cellular functions can lead to various clinical outcomes, including manual deficits per lineage.

Signs:
- Frequent infections, chronic issues, unusual organisms.
- Growth retardation and a notable family history.

Humoral Immunodeficiency:
- Characterized by recurrent infections due to bacteria (especially encapsulated).
Cell-Mediated Immunodeficiency:
- Marked by infections from viruses, fungi, and opportunistic organisms.

Incidence:
- ~50,000 cases in the population.
- Higher male prevalence (5:1 in infants, 1:1 in adults).
Pathogenic Issues:
- Result from abnormal genes leading to defective protein production and cell differentiation.

58% of diagnoses occur in children under 15.
83% of these cases involve males.
Inheritance modes include X-linked recessive, autosomal recessive, autosomal dominant, and sporadic cases.

Table 18-1: Lists of specific immunodeficiency diseases, their genetic defects, immune impacts, and inheritance patterns including:
- Severe Combined Immunodeficiency (SCID) - RAG1/RAG2 defects, leading to no TCR gene rearrangement.
- Common gamma-chain deficiencies affecting cyokine signaling and leading to T and NK cell developmental issues.
- Agammaglobulinemias - Blocked development of B cells, resulting in few or no mature cells.

Table 18-2: Patterns of infections caused by various immunodeficiency disorders.
Common opportunistic infections relative to specific disorders (e.g., antibody deficiencies linked to recurrent infections).
Clinical Features of SCID: Poor growth, susceptibility to infections, chronic diarrhea, and absence of lymphoid tissue.

MHC defects resembling SCID result in poor responses to infections, highlighting the importance of MHC Class I and II.

DiGeorge Syndrome: Developmental defects due to chromosomal deletions affecting immune competency.
Wiskott-Aldrich Syndrome: Defect in cytoskeletal function leading to eczema, infection susceptibility, and autoimmune risks.

David Vetter's story as the first SCID-X1 survivor living in containment; issues arising from lack of IL-2RG.

Transition from confinement to modern therapies such as bone marrow transplants and gene therapy.

Overview of recent advances in gene therapy for the treatment of immunodeficiencies.

Discussion on common variable immunodeficiency (CVID) impacts and treatment strategies.
Specific disorders (like X-linked agammaglobulinemia) described in detail with clinical manifestations.
Chronic Granulomatous Disease: Impaired ROS generation leading to higher infection susceptibility.

Treatment strategies from passive immunization to gene therapies.
Challenges faced, including adverse effects leading to complications like leukemia.