Human immunodeficiency virus (HIV) is a lentivirus (a member of the retrovirus family) that causes acquired immunodeficiency syndrome (AIDS), a condition in humans in which the immune system begins to fail, leading to life-threatening opportunistic infections. Infection with HIV occurs by the transfer of blood, semen, vaginal fluid, pre-ejaculate, or breast milk. Within these bodily fluids, HIV is present as both free virus particles and virus within infected immune cells.
Severe combined immunodeficiency (SCID), or Boy in the Bubble Syndrome, (also known as "Alymphocytosis," "Glanzmann–Riniker syndrome," "Severe mixed immunodeficiency syndrome," and "Thymic alymphoplasia") is a genetic disorder in which both "arms" of the adaptive immune system are crippled, due to a defect in one of several possible genes. SCID is a severe form of heritable immunodeficiency.
Immunodeficiency (or immune deficiency) is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Most cases of immunodeficiency are acquired ("secondary") but some people are born with defects in the immune system, or primary immunodeficiency. Transplant patients take medications to suppress their immune system as an anti-rejection measure, as do some patients suffering from an over-active immune system.
Adenosine deaminase deficiency, also called ADA deficiency or ADA-SCID, is an autosomal recessive metabolic disorder that causes immunodeficiency. It accounts for about 15% of all cases of severe combined immunodeficiency (SCID). ADA deficiency may be present in infancy, childhood, adolescense, or adulthood. Age of onset and severity is related to some 29 known genotypes associated with the disorder.
Common variable immunodeficiency (CVID) (also known as Acquired hypogammaglobulinemia) is a group of 20–30 primary immunodeficiencies (PIDs), which have a common set of symptoms but which have different underlying causes. Common variable immunodeficiency is the most commonly encountered primary immunodeficiency.
Acquired immune deficiency syndrome or acquired immunodeficiency syndrome (AIDS) is a disease of the human immune system caused by the human immunodeficiency virus (HIV). This condition progressively reduces the effectiveness of the immune system and leaves individuals susceptible to opportunistic infections and tumors.
Idiopathic CD4+ lymphocytopenia (ICL) is a very rare medical syndrome. In this condition, the body has too few CD4+ T lymphocytes, which are a kind of white blood cell. It is sometimes mischaracterized as "HIV-negative AIDS" by AIDS denialists, though in fact its clinical presentation differs from that seen with HIV/AIDS. People with ICL have a weakened immune system and are susceptible to opportunistic infections, although the rate of infections is lower than in people with AIDS.
Nezelof syndrome (also known as "Thymic dysplasia with normal immunoglobulins") is an autosomal recessive congenital immunodeficiency condition due to underdevelopment of the thymus. An association with CD44 has been proposed.
Primary immunodeficiencies are disorders in which part of the body's immune system is missing or does not function properly. To be considered a primary immunodeficiency, the cause of the immune deficiency must not be secondary in nature (i.e. , caused by other disease, drug treatment, or environmental exposure to toxins).
Complement deficiency is a condition of absent or suboptimal functioning of one of the complement system proteins. The disorders can be divided into two categories: Disorders of the proteins which act to inhibit the complement system can lead to an overactive response, causing conditions such as hereditary angioedema and hemolytic-uremic syndrome.
Severe Combined Immunodeficiency (SCID) is a severe immunodeficiency genetic disorder that is characterized by the complete inability of the adaptive immune system to mount, coordinate, and sustain an appropriate immune response, usually due to absent or atypical T and B lymphocytes. In humans, SCID is colloquially known as "bubble boy" disease, as victims may require complete clinical isolation to prevent lethal infection from environmental microbes.