World Immunodeficiency Week is observed every year in April to raise awareness about primary immunodeficiencies and improve their diagnosis and treatment. Immunodeficiency disorders occur when the body's immune response is reduced or absent, and mostly happen when special white blood cells called T or B lymphocytes, or both, do not function normally, or the body does not produce enough antibodies.
A failure or absence of different elements of the immune system, which include lymphocytes, phagocytes, which are types of immune cells that can surround and kill microorganisms, ingest foreign substances, and remove dead cells, and the complement system, which is a part of the immune system that cleans up damaged cells, helps the body heal after an injury or infection, and destroys pathogens, results in immunodeficiency diseases.
Primary immunodeficiency diseases are rare, genetic disorders that impair and weaken the immune system, and allow infections and other health problems to occur more easily.
How common are primary immunodeficiencies in India?
In the United States, one in 1,200 live births is estimated to have primary immunodeficiency. On the basis of this, experts estimate that more than one million Indians are likely to have primary immunodeficiency diseases.
"Based on a study from the Post Graduate Institute of Medical Education & Research, Chandigarh, the most common primary immunodeficiency diseases are X-linked Agammaglobulinemia, severe combined immunodeficiency, chronic granulomatous disease, Wiskott-Aldrich syndrome, and common variable immunodeficiency," Dr Sunit Chandra Singhi, Head, Department of Paediatrics, Amrita Hospital, Faridabad, told ABP Live.
Some experts say that one in every 5,000 to 10,000 live births in India has primary immunodeficiency. Selective IgA deficiency, a disease in which one lacks or does not have enough Immunoglobulin A, an antibody body that protects mucosal tissues from microbial invasions, and common variable immunodeficiency are the most frequently primary immunodeficiency diseases seen in India.
“The prevalence of primary immunodeficiency diseases in India is unknown, but it is considered to be similar to that of other parts of the world, at roughly one in every 5,000 to 10,000 live births. Primary antibody deficiency disorders, such as common variable immunodeficiency and selective IgA deficiency are the most frequent primary immunodeficiency diseases seen in India. Severe combined immunodeficiency, Wiskott-Aldrich syndrome, and chronic granulomatous disease are some less prevalent primary immunodeficiency diseases reported in India,” Varun Sheth, Co-Founder and CEO of Ketto India, told ABP Live.
He also said that it is vital to highlight that many cases of primary immunodeficiency diseases in India may go undetected or misdiagnosed due to a lack of knowledge and diagnostic facilities. “As a result, increasing awareness, early identification, and treatment of primary immunodeficiency diseases is crucial to improving outcomes for those affected,” Seth said.
All about the immunodeficiency diseases commonly seen in North India
The condition in which the immune system has low or absent B cells and immunoglobulins is known as agammaglobulinemia.
According to the United States' National Institutes of Health (NIH), X-linked Agammaglobulinemia, also known as Bruton type Agammaglobulinemia, Congenital Agammaglobulinemia, or X-linked Infantile Agammaglobulinemia is an inherited immune disorder caused by an inability to produce B lymphocytes or the immunoglobulins or antibodies that B cells make. This disease is caused by a genetic mutation, and reduces the ability of the immune system to fight infections. It is characterised by infections of the inner ear, respiratory tract, sinuses, internal organs and bloodstream.
The disease mostly affects males, and is usually diagnosed in infancy or early childhood.
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Severe combined immunodeficiency, also known as Swiss-type agammaglobulinemia is a group of rare disorders caused by mutations in different genes involved in the development and function of infection-fighting immune cells, and is characterised by the combined absence of T and B lymphocyte function, leading to extreme susceptibility to very serious infections, and symptoms such as pneumonia, blood infection, repeated ear infections, chronic skin infections, diarrhoea, test infections in the mouth, and liver infection.
Chronic granulomatous disease is a genetic disorder in which phagocytes are unable to kill certain types of bacteria and fungi, causes the immune system to malfunction, resulting in a form of immunodeficiency, and is characterised by recurrent bacterial and fungal infections, and inflammation or granulomas in various tissues.
Wiskott-Aldrich syndrome is a primary immunodeficiency disease characterised by abnormal immune system function, a reduced ability to form blood clots, and eczema, which is an inflammatory skin disorder in which abnormal patches of red, irradiated skin are formed, according to NIH. The disease primarily affects males, and is characterised by easy bruising or bleeding due to a decrease in the number and size of platelets, an increased risk of some cancers such as lymphoma, and susceptibility to inflammatory disorders. It is a genetic disorder.
Common variable immunodeficiency is a primary immunodeficiency disease characterised by low levels of protective antibodies, which renders the immune system unable to defend the body against bacteria and viruses, and results in recurrent and severe infections primarily affecting the sinuses, respiratory tract and ears, together called sinopulmonary infections. The antibody deficiency usually occurs in adults, but can also take place in children, and is also known as hypogammaglobulinemia.
Classes of primary immunodeficiency diseases
According to the 2019 International Union of Immunological Societies Expert Committee, there are about 404 primary immunodeficiency diseases in the world. Dr Sanghi said that they are divided into the following 10 classes:
- Combined immunodeficiencies
- Combined immunodeficiencies with syndromic features
- Predominantly antibody deficiencies
- Diseases of immune dysregulation
- Congenital defects of phagocytes
- Defects in intrinsic and innate immunity
- Autoinflammatory diseases
- Complement deficiencies
- Phenocopies of inborn errors of immunity
- Genes that cause bone marrow failure
Combined immunodeficiencies are the result of defective development or function of T cells, are the most severe form of primary immunodeficiency diseases, and are characterised by increased susceptibility to infection. Since T cells are affected, antibody production decreases. B cells and natural killer cells may also be affected due to combined immunodeficiencies.
According to Dr Sanghi, combined immunodeficiencies with syndromic features are primary immunodeficiency disorders in which defective mutation not only causes defects in circulating immune cells, but also affects the function of other organs. This results in clinical features other than immune deficiency, such as eczema and abnormal facial development.
Predominantly antibody deficiencies are the most common type of primary immunodeficiency in adults, and are characterised by a reduced number of B cells and immunoglobulins.
Diseases of immune dysregulation are those in which the body cannot control or restrain an immune response, and the body either under-reacts to foreign invaders, or overreacts to foreign antigens, as a result of which the immune cells attack healthy cells and tissues.
According to a study published in the journal Cellular Primary Immunodeficiencies, defects in intrinsic and innate immunity are a group of monogenic diseases (diseases caused by differences in a single gene) in which there is a defect in the cellular components of innate immunity, which are not included in phagocyte defects or complement defects. They are often characterised by oral manifestations including oral infections such as candidiasis and oral lesions.
Autoinflammatory diseases are conditions in which the immune system inappropriately triggers episodes of inflammation, mostly due to genetic mutations, and are problems occurring within the innate immune system. Since the immune cells target the body's own cells, one can suffer from symptoms such as fever, joint swelling, or rash, and also a condition called amyloidosis, which is a potentially fatal build-up of blood protein in vital organs.
Complement deficiencies are primary immunodeficiencies that result in various clinical scenarios depending on the specific complement protein that is deficient, and can include an increased risk of a wide range of infectious, inflammatory and thrombotic conditions (conditions in which blood clots block veins or arteries). Complement proteins are plasma proteins that interact with one another to opsonize pathogens, or make them susceptible to phagocytosis, and induce a series of inflammatory responses, helping fight infections.
Phenocopies of inborn errors of immunity are a special group of immune deficiencies caused by somatic mutations, rather than genomic mutations, or are autoantibodies (antibodies made against substances produced by a person's own body, and can be pathogenic) against cytokines (small proteins thF control growth, activity and communications of different immune cells), resulting in clinical manifestations similar to other primary immunodeficiency diseases.