Types of PI

Primary Immunodeficiency (PI) is an umbrella term for over 300 genetic defects and disorders of the immune system recognized by the World Health Organization. Together they affect approximately 29,000 Canadians. Primary Immunodeficiency is not considered a rare disease as a category, but each individual form of PI is rare.

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There are 5 names in this directory beginning with the letter H.
Heavy Chain Deficiencies
Heavy Chain Deficiencies are when multiple genes that code for immunoglobulins (IgA, IgG1, IgG2, etc.) are missing from the body. Individuals with this condition can only make one or only a few types of immunoglobulin, which may result in a susceptibility to infections. However, it is possible for individuals with Heavy Chain Deficiencies to be asymptomatic. Credits: Immune Deficiency Foundation

Hoyeraal-Hreidarsson Syndrome (Dyskeratosis Congenita)
Hoyeraal-Hreidarsson Syndrome has X-linked inheritance and is a severe form of Dyskeratosis Congenita. Symptoms of the condition include poor growth inside the womb, microcephaly (small head), pancytopenia (low numbers of all blood cells), and decreased natural killer cells. Individuals with the condition are heavily susceptible to infections. Accurate diagnosis of Dyskeratosis Congenita is critical to ensure proper treatment, because patients who have DC do not respond to immunosuppressive therapy. Although the exact probability of Hoyeraal-Hreidarsson Syndrome is unknown, it is estimated that the more general condition Dyskeratosis Congenita occurs in approximately 1 in 1 million people. Credits: Immune Deficiency Foundation, Genetics Home Reference

Human Natural Killer Cell Deficiencies
Natural killer (NK) cells are innate immune cells that are significant in the killing of viral cells. These cells are especially significant in the defense against the herpes viruses, including Herpes simplex virus (oral and genital), Epstein-Barr virus (causing infectious mononucleosis), and the varicella virus (chicken pox and shingles). Individuals with Human Natural Killer Cell Deficiencies will be more vulnerable to these viruses. Human NK cell deficiencies are separated into two major categories of classical NK cell deficiency (quantitative defects) and functional NK cell deficiency (qualitative defects). Quantitative defects mean there is a decreased number of NK cells in the peripheral blood. Qualitative defects mean there are a normal number of NK cells in the blood, but they have abnormal function. Credits: Immune Deficiency Foundation

Hyper IgE Syndrome
Hyper IgE Syndrome, also known as Job syndrome, is a rare form of primary immunodeficiency. Major symptoms of the condition are frequent infections related to the lungs, inflammation, skin infections, and high levels of the immune system protein immunologlobulin E. Other symptoms relate to the bones and teeth, resulting in the possibility of skeletal abnormalities, scoliosis, and low bone density. Baby teeth also may not fall out to make room for the adult set of teeth. Hyper IgE Syndrome can be autosomal dominant (AD) or autosomal recessive (AR). The condition is estimated to affect less than 1 in a million people. Credits: Immune Deficiency Foundation

Hyper IgM Syndromes
Hyper IgM Syndrome (HIGM) is a result of decreased levels of the antibodies IgG and IgA, but a normal or increased level of IgM in blood. Individuals with Hyper IgM are susceptible to recurrent and severe infections. Most individuals with the syndromeare diagnosed within the first or second year of life. Pneumonia, sinusitis, and otitis (ear infection) are common infections for those with HIGM. Other common issues are chronic diarrhea, malabsorption of nutrients, and a failure to thrive (gain weight and grow). They are also at a higher risk of being diagnosed with cancer, specifically lymphoma. The most common form of the syndrome X-chromosome linked, meaning it is primarily found in males. X-linked Hyper IgM syndrome is estimated to occur in every 2 per million newborn males. Credits: Immune Deficiency Foundation, Genetics Home Reference
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