Adenosine Deaminase Deficiency (ADA deficiency) is a rare genetic disorder that affects the immune system. It occurs when the body lacks the enzyme adenosine deaminase, which is crucial for breaking down toxic substances in the body. Without this enzyme, toxic levels of adenosine build up, leading to severe immune system problems. Individuals with ADA deficiency often experience recurrent infections and may develop severe combined immunodeficiency (SCID). This condition is typically diagnosed in infancy and can be treated with enzyme replacement therapy or a bone marrow transplant. Early diagnosis and intervention are essential for improving health outcomes.