What Causes Lymphedema?
People can be born with abnormalities in the lymphatic system. This type of lymphedema is known as primary lymphedema, which can impact any part of the body and may involve swelling in multiple limbs or body regions. Because primary lymphedema may be associated with many other congenital or genetic abnormalities, babies or children with lymphedema should be referred to a genetic counselor to help determine whether additional testing is needed for the child or the family. For example, Milroy’s disease includes primary lymphedema but may also associated with arterial-venous abnormalities such as hemangioma or lymphangioma, or other genetic conditions such as Klippel-Trenaury Syndrome or Park-Weber Syndrome.
The most common form of primary lymphedema is lymphedema praecox which appears during puberty, occurs mostly in girls, and usually affects one or both lower extremities. Lymphedema tarda, another form of primary lymphedema, begins later in life and usually affects both lower extremities in men and women.
Secondary lymphedema occurs as a result of damage to the lymphatic system. Common causes include surgery, trauma, radiation, or infection. After cancer treatment in particular, secondary lymphedema may develop immediately or even months to years later. Venipuncture with a needle stick increases the risk of developing secondary lymphedema, so blood draws or IV catheter placement should be avoided in the arm or leg on the site cancer treatment occurred. The same is true for injections and chemotherapy, as these should be avoided in the limb treated for previous cancer—including the arm on the side where shoulder/axillary lymph node dissection occurred for breast cancer.
Specific cancer-related surgeries such as surgical resection of melanoma, breast, gynecological, head and neck, prostate or testicular, bladder, or colon cancer may require the removal of lymph nodes. These surgeries put patients at risk of developing secondary lymphedema. To minimize this risk, surgeons may opt for a Sentinel Lymph Node Biopsy (SLNB) whenever possible. This procedure removes only one or two lymph nodes that specifically drain the tumor site. If these nodes are benign, no further nodes are removed. While the SLNB greatly diminishes the risk of lymphedema, it does disrupt the lymphatic system and still puts the patient at some risk for developing lymphedema. Other non-cancer-related surgeries or trauma can also disrupt lymphatic pathways, resulting in lymphatic impairment and leading to the onset of lymphedema.
Radiation therapy can damage otherwise healthy lymph nodes and vessels, and can cause scarring of the lymphatic vessels which leads to fibrosis and subsequently diminish lymphatic flow. The extent of tissue being irradiated generally determines the additional lymphedema risk. While receiving radiation it is important to closely monitor the radiated area for discoloration, redness or erythema or blisters. If swelling is present before radiation, lymphedema treatment is recommended to keep it from getting worse during radiation therapy.
The previously mentioned causes of lymphedema are considered direct causes because of the permanent structural change that can result from surgery, trauma, or radiation. However, other conditions may also contribute to developing lymphedema by causing inflammation in an area at risk of swelling. Inflammation brings additional fluid and scarring into the limb—both of which place an additional burden on the lymphatic system. Infections such as lymphangitis or cellulitis may lead to progressive swelling and scarring, even when they appear to be minor. As a result, prevention of inflammation through rigorous skin care and avoidance of injections/blood draws (as mentioned earlier) is vital to reduce the risk of lymphedema. Refer to the Skin Care Recommendations in the Risk Reduction Guidelines. Another cause of inflammation may be from parasite infections such as filariasis, where filarial worms are transmitted through mosquito bites followed by worm growth and obstruction of lymphatic channels. The severe lymphedema seen in arms, legs, or genitalia is also called elephantiasis, and affects more than 250 million people in the endemic areas of Southeast Asia, India, and Africa.