Lymphedema is an accumulation of lymphatic fluid in the interstitial tissue that causes swelling, most often in the arm(s) and/or leg(s), and occasionally in other parts of the body. Primary lymphedema can develop when lymphatic vessels are missing or impaired, which may be congenital. Secondary lymphedema arises when lymph nodes are removed, or when lymph vessels are damaged due to parasitic infections in unsanitary conditions.
When the impairment becomes so great that the lymphatic fluid exceeds the lymphatic transport capacity, an abnormal amount of fluid collects in the tissues of the affected area. Left untreated, this stagnant, protein-rich fluid not only causes tissue channels to increase in size and number, but also reduces oxygen availability in the transport system, interferes with wound healing, and provides a culture medium for bacteria that can result in lymphangitis infection and possibly death.
Although lymphoedma is hard to diagnose, looking at recent estimates, it is as common as Alzheimer’s disease, four times as common as HIV and rheumatoid arthritis, and twelve times as common as multiple sclerosis.
According to a report put out by the Lymphatic Network: "Worldwide, one of the most common causes of lymphoedema is filariasis. It occurs in tropical climates only, but the World Health Organisation estimates that 120 million people are infected with the disease and of those, 40 million have lymphoedema or another related problem such as hydrocele (lymph fluid collecting in the sac around the testicles)."