Immune Deficiency Disorders: Types

An immunodeficiency can cause frequent and recurrent infections of varying severity. The disorder may be due to underlying medical conditions or treatments for these conditions. 

This is termed secondary (acquired) immunodeficiency and is a much more common reason for recurrent infections in adults. A less common cause is primary (congenital) immunodeficiency, which typically presents in infancy or early childhood.

Primary Immunodeficiency

Inborn errors of immunity, also called Primary Immunodeficiency Disorders (PIDD), refer to genetic abnormalities of the immune system. Primary immunodeficiency can involve problems with T-cells, B-cells, phagocytic cells or the complement system. Due to advances in genetic sequencing, we know that there are more than 430 known inborn errors of immunity and more are identified by researchers every year.

Most primary immune deficiencies tend to run in families, but not always. Examples include X-linked agammaglobulinemia (XLA), severe combined immunodeficiency (SCID), and DiGeorge syndrome. Other primary immune deficiencies, such as common variable immunodeficiency (CVID), have a complicated genetic inheritance and sometimes a causative gene mutation is not found. Sometimes there is a problem with gene expression or the interaction between proteins that is not found in the DNA sequence. This is an area of active research.

Acquired Immunodeficiency

Acquired, or secondary, immunodeficiency occurs when the function of the immune system is disrupted secondary to an underlying disease, medications, surgery or other medical procedure. It is more common than primary immunodeficiency. Leukemia or multiple myeloma are diseases that crowd out the normal stem cells of the bone marrow and can lead to abnormally-functioning B-cells. Medications such as chemotherapies for cancer and immunosuppressants for autoimmune diseases can weaken the immune system, as well. Some examples of these drugs include cyclophosphamide, mycophenolate mofetil, azathioprine and rituximab. Chronic infections also can weaken the immune system. For example, Human Immunodeficiency Virus (HIV) can cause a disease called Acquired Immune Deficiency Syndrome (AIDS). HIV is a sexually transmitted disease that can be spread via contact with infected materials such as needles and through breast milk. Radiation and burns also can result in immune deficiency. Removal of one’s spleen (e.g., due to an accident or injury or due to an underlying medical issue) can cause immunodeficiency, as well.