Persistent generalized lymphadenopathy

The lymphatic system is part of the immune surveillance system. Blood contains fluid and blood cells. The fluid, which may contain suspended foreign material such as bacteria and viruses, seeps through blood vessel walls into the tissues, where it bathes the body cells and exchanges substances with them. Some of this lymph fluid is then taken up by lymphatic vessels and passed back to the heart, where it is again mixed with the blood. On its way, the fluid passes through the lymph nodes, small nodular organs located throughout the body but concentrated in certain areas such as the armpits or groin. These lymph nodes are also known as "glands" or "lymphoid tissue". If they detect something foreign passing through them, they enlarge. This is called "lymphadenopathy" or "swollen glands". Usually this is localised (for example, an infected spot on the scalp will cause lymph nodes in the neck on that same side to swell). However, when two or more lymph node groups are involved, it is called "generalized lymphadenopathy". Usually this is in response to a significant systemic disease and will subside once the person has recovered. Sometimes it can persist long-term, even when no explanation for the lymphadenopathy can be found. This is then called persistent generalized lymphadenopathy (PGL).

PGL is often found in cases of autoimmune disease (where the body is attacking itself). These include diseases such as rheumatoid arthritis, lupus and sarcoidosis. Some forms of cancer will also cause PGL. Sometimes, despite exhaustive investigation, no cause for PGL is found. For the patient and the physician, this can continue to be a source of concern, but many adults have had PGL all their lives and suffered no ill effects. In others, the PGL may persist for a decade or more and then mysteriously subside. Children often have generalised lymphadenopathy of the head and neck, or even PGL, without the finding of a sinister cause. At puberty this usually disappears.

The immune system of some people may be sensitised by exposure to a living exogenous irritant such as a bacterial or viral infection, which then results in PGL after the organism has been cleared from the body. In some cases the sensitisation is caused by non-living exogenous irritants such as cyclic hydrocarbons (for example, resinous vapours) or pesticides and herbicides.