_IMMUNODEFICIENCY DISORDERS
Components
of the immune system, innate or acquired can be
absent or abnormal leading to immunodeficiency states which
may be trivial to fatal. Infections are common, often by opportunists. Autoantibodies with or without
autoimmune disease, and development of
malignancy have been recorded with high incidence.
Classification
Immunodeficiencies are classified into primary Immunodeficiency disorders which are genetically determined, and secondary immunodeficiency disorders.
A. Primary Immunodeficiency Disorders
1. Deficiency of Innate Immunity
(a) Phagocytic cell defects
(b) Complement system deficiencies
2. Primary deficiency in Acquired Immunity
(a) Primary B cell deficiency
(b) Primary T cell deficiency
(c) Combined B and T cell deficiency
B. Secondary Immunodeficiency Disorders
1.Acquired Immunodeficiency Syndrome- AIDS
2. Secondary consequences by many factors like malnutrition, viral infections, lymphoproliferative disorders, X-rays, cytotoxic drugs.
Classification
Immunodeficiencies are classified into primary Immunodeficiency disorders which are genetically determined, and secondary immunodeficiency disorders.
A. Primary Immunodeficiency Disorders
1. Deficiency of Innate Immunity
(a) Phagocytic cell defects
(b) Complement system deficiencies
2. Primary deficiency in Acquired Immunity
(a) Primary B cell deficiency
(b) Primary T cell deficiency
(c) Combined B and T cell deficiency
B. Secondary Immunodeficiency Disorders
1.Acquired Immunodeficiency Syndrome- AIDS
2. Secondary consequences by many factors like malnutrition, viral infections, lymphoproliferative disorders, X-rays, cytotoxic drugs.
Primary Immunodeficiency Disorders
These occur as a result of a defect in differentiation in the immune system. Bacterial infection is common with defects in phagocytic cells, complement pathways or B cell system. Viral and fungal infections are common with T cell deficiencies.
I. Phagocytic cell defects. Neutrophilic Defects :
1.Quantitative defects Neutropenia or granulocytopenia.
2. Qualitative defects The defect may be in chemotaxis,ingestion or killing and digestion by phagocytic cells.
(a) Chronic granulomatous disease (CGD). It is an X-linked recessive disorder in first 2 years of life due to defect in enzymatic inability to generate oxygen metabolites. Recurrent infection occur by Staphylococcus and Escherichia.
(b) Myeloperoxidase deficiency.
(c) Other disorders like leucocyte adhesion deficiency, Chediak-Higashi syndrome, Lazy leucocyte syndrome.
II. Complement deficiency
1. C1 esterase inhibitor deficiency cause hereditary angioedema characterized by recurrent transient localized oedema. Kinin is produced which increases capillary permeability.
2. Clq deficiency leads to repeated infections.
3. C2 and C4 deficiencies can cause disorder similar to SLE.
4. C3 deficiency results in pyogenic infections, particularly with Neisseria meningitides and Streptococcus pneumoniae,
5. C5 deficiency leads to bacterial infection,
6. C6, C7 and C8 deficiencies lead to increased susceptibility to meningococcal and gonococcal infections.
III. B cell deficiency disorders
Bruton's congenital (X-linked) agammaglobulinaemia, common variable hypogammaglobulinaemia, selective IgM deficiency, selective IgA deficiency.
IV. T cell deficiency disorders
DiGeorge syndrome (Thymic hypoplasia) results from failure of thymic development.
V. Combined B cell and T cell deficiency disorders Severe combined immunodeficiency disease (SCID), ataxia telangiectasis, Wiskott-Aldrich syndrome.
_
These occur as a result of a defect in differentiation in the immune system. Bacterial infection is common with defects in phagocytic cells, complement pathways or B cell system. Viral and fungal infections are common with T cell deficiencies.
I. Phagocytic cell defects. Neutrophilic Defects :
1.Quantitative defects Neutropenia or granulocytopenia.
2. Qualitative defects The defect may be in chemotaxis,ingestion or killing and digestion by phagocytic cells.
(a) Chronic granulomatous disease (CGD). It is an X-linked recessive disorder in first 2 years of life due to defect in enzymatic inability to generate oxygen metabolites. Recurrent infection occur by Staphylococcus and Escherichia.
(b) Myeloperoxidase deficiency.
(c) Other disorders like leucocyte adhesion deficiency, Chediak-Higashi syndrome, Lazy leucocyte syndrome.
II. Complement deficiency
1. C1 esterase inhibitor deficiency cause hereditary angioedema characterized by recurrent transient localized oedema. Kinin is produced which increases capillary permeability.
2. Clq deficiency leads to repeated infections.
3. C2 and C4 deficiencies can cause disorder similar to SLE.
4. C3 deficiency results in pyogenic infections, particularly with Neisseria meningitides and Streptococcus pneumoniae,
5. C5 deficiency leads to bacterial infection,
6. C6, C7 and C8 deficiencies lead to increased susceptibility to meningococcal and gonococcal infections.
III. B cell deficiency disorders
Bruton's congenital (X-linked) agammaglobulinaemia, common variable hypogammaglobulinaemia, selective IgM deficiency, selective IgA deficiency.
IV. T cell deficiency disorders
DiGeorge syndrome (Thymic hypoplasia) results from failure of thymic development.
V. Combined B cell and T cell deficiency disorders Severe combined immunodeficiency disease (SCID), ataxia telangiectasis, Wiskott-Aldrich syndrome.
_
_ Secondary Immunodeficiency Disorders
This can lead to an increased susceptibility to opportunist infections.
1. Acquired immune deficiency syndrome (AIDS).
2. Other conditions :
(a)Occurs as complications of infections (like measles, influenza and infectious mononucleosis), malnutrition, aging.
(b) Occurs as side effects of immunosuppression: corticosteroids, irradiation or chemotherapy for cancer, and autoimmune diseases.
This can lead to an increased susceptibility to opportunist infections.
1. Acquired immune deficiency syndrome (AIDS).
2. Other conditions :
(a)Occurs as complications of infections (like measles, influenza and infectious mononucleosis), malnutrition, aging.
(b) Occurs as side effects of immunosuppression: corticosteroids, irradiation or chemotherapy for cancer, and autoimmune diseases.