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Immunodeficiency refers to a state where the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. It can be primary (congenital) due to genetic defects, or secondary (acquired) resulting from external factors like medications, infections, or malignancies.
Primary immunodeficiencies result from inherited genetic mutations affecting immune cell development, function, or signaling pathways, such as severe combined immunodeficiency (SCID) or common variable immunodeficiency. Secondary immunodeficiencies occur when external factors damage or suppress immune function, including HIV infection depleting CD4+ T cells, chemotherapy destroying immune cells, or chronic diseases like diabetes impairing immune responses.
Patients with immunodeficiency present with recurrent, severe, or unusual infections that are often caused by opportunistic pathogens rarely seen in healthy individuals. The pattern of infections provides diagnostic clues - bacterial infections suggest antibody deficiency, while viral/fungal infections indicate cellular immune dysfunction. Early recognition is crucial as these patients require prompt antimicrobial therapy, immunoglobulin replacement, and in some cases, bone marrow transplantation.