From the Guidelines
Immune disorders are primarily classified into two broad categories: innate and adaptive, with further subdivisions based on the principal immunologic mechanisms disrupted and dominant clinical features, as outlined in the practice parameter for the diagnosis and management of primary immunodeficiency 1. The classification of immune disorders is crucial for determining the appropriate diagnostic approaches and treatment strategies.
Classification of Immune Disorders
- Primary immunodeficiency disorders (PIDDs) result from inherited genetic defects that affect the immune system and immune responses, and can be subdivided into:
- Humoral or antibody PIDDs, which account for approximately half of all PIDDs
- Combined B- and T-cell defects
- Phagocyte defects
- Diseases of immune dysregulation
- Disorders of innate immunity, including NK cell defects
- Autoinflammatory disorders
- Complement deficiencies
- Secondary immunodeficiencies develop due to external factors like HIV infection, malnutrition, or medications that suppress immunity.
- Autoimmune disorders occur when the immune system mistakenly attacks healthy tissues.
- Hypersensitivity disorders represent exaggerated immune responses to normally harmless substances.
Key Considerations
- The true incidence of PIDDs is unknown, but estimated incidences vary from 1 in 10,000 to 1 in 2,000 live births, with a prevalence of 1 in 10,000 to 1 in 12,000 in the general population 1.
- Understanding the classification of immune disorders is essential for clinicians to determine the appropriate diagnostic approaches and treatment strategies, which may include immunosuppressants, immunoglobulin replacement, or antihistamines and corticosteroids, depending on the exact disorder, its severity, and individual patient factors.
- The male/female ratio of PIDDs is approximately 5:1 in infants and children, but approaches 1:1 in adults, as noted in the practice parameter for the diagnosis and management of primary immunodeficiency 1.
- A list of PIDDs, including their genetic defects and clinical features, is provided in Table E2 of the practice parameter for the diagnosis and management of primary immunodeficiency 1, and further detailed in the classification of primary immunodeficiencies 1.
From the Research
Classification of Immune Disorders
The classification of immune disorders can be based on various factors, including the type of immune response, the nature and location of the antigen, and the principal pathogenic mechanism responsible for cell and tissue injury.
- Immunological diseases can be subdivided into two main groups:
- Autoimmune diseases can be divided into primary autoimmune diseases, in which the immune system is over-reactive, and secondary autoimmune diseases, in which the immune system is normal but some autoantigens are slightly altered 3
- Primary autoimmune diseases can be further divided into organ-specific autoimmune diseases, such as thyroiditis and gastritis, and generalized autoimmune diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis 3
- Monogenic autoimmune diseases, such as autoimmune polyendocrinopathy candidiasis and ectodermal dystrophy, are characterized by autoimmunity and immune deficiency due to single gene defects 4
- Primary immune regulatory disorders (PIRDs) comprise a heterogeneous group of monogenic disorders that impact homeostatic control of inflammation and immune tolerance, and can be categorized into multiple autoimmune diseases, immune dysregulation with colitis, disorders with hemophagocytic lymphohistiocytosis (HLH) and/or Epstein Barr virus (EBV) susceptibility, autoinflammatory syndromes, type 1 interferonopathies, and disorders of sterile inflammation 5
- Autoimmune diseases can also be classified as systemic or organ-specific, although this categorization is not based on causative pathogenic factors 6