AAIQ   The Association of Allergists and Immunologists of Québec

Secondary immunodeficiency

The immune system is composed of a variety of cells, especially white blood cells, and proteins, for which one of the principal functions is microbial defense. A deficit in the immune system can therefore lead to unusually severe or uncommon recurrent infections. Immune deficits (immunodeficiency) may be primary or secondary. Secondary immune deficiencies or acquired deficiencies, more frequent than primary immune deficiencies, are problems of the immune system that are not genetic and which are caused by external factors.

An example of a secondary immune deficiency: AIDS

The most well-known example of a secondary immune deficiency is the immunodeficiency caused by the human immunodeficiency virus, or HIV. HIV attacks certain cells in the immune system and prevents them from carrying out their proper functions against microbes. When the immune system is sufficiently weakened, infected people catch atypical and severe infections. This is then called the Acquired Immunodeficiency Syndrome, or AIDS. AIDS at this time is often treated by a specialized multidisciplinary team.

What are other causes of secondary immunodeficiency?

Other causes of secondary immunodeficiency include: severe malnutrition, certain chronic diseases such as diabetes, immunosuppressive medication or chemotherapy, certain cancers such as leukemia, and the absence of the spleen (sometimes the spleen must be removed because of trauma, for example).

How are secondary immunodeficiencies treated?

The treatment depends on the severity in the deficiency of the immune system. Treatment of the underlying cause often leads to improvement of the condition. Administration of immunoglobulins and antibioprophylaxis may also be useful in some cases.


Nha Uyen Nguyen-Luu, MD FRCPC
(translation: Andrew Moore, MD FRCPC)