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Harvard Medical School

Lymphedema

What Is It?

Lymphedema is the buildup of fluid called lymph in the tissues under your skin when something blocks its normal flow. This causes swelling, most commonly in an arm or leg.

Lymph normally does an important job for your body. It carries foreign material and bacteria away from your skin and body tissues, and it circulates infection-fighting cells that are part of your immune system. Lymph flows slowly through the network of vessels called your lymphatic system, stopping at points along the way to be filtered through lymph nodes (small bean-shaped organs that are part of your immune system). Lymph first collects by seeping out of your cells into the smallest lymphatic vessels near the skin. After traveling through these small vessels, lymph drains into deeper, wider lymph channels that run through the body. Eventually, lymph fluid returns to the blood.

Lymphedema is not the same as edema, which is another condition that causes arm or leg swelling. In both problems there is too much fluid in the limb, but only lymphedema results from blocked drainage. Without a blockage, the fluid can be pushed forward in your lymphatic system, so you can see pitting — small temporary indentations left on the skin after you press on the swollen area. Pitting does not happen when you press on skin if you have lymphedema.

In most cases of lymphedema, the lymphatic system has been injured so that the flow of lymph is blocked either temporarily or permanently. This is called secondary lymphedema. Common causes include:

• Surgical damage — Surgical cuts and the removal of lymph nodes can interfere with normal lymph flow. Sometimes, lymphedema appears immediately after surgery and goes away quickly. In other cases, lymphedema develops from one month to 15 years after a surgical procedure. Lymphedema is most commonly seen in people who have had surgery for breast cancer. It develops in up to 25% of those who have a breast removed (mastectomy) along with the lymph nodes under the arm. The risk doubles for those who also receive radiation treatments to the underarm area. Lymphedema also may occur after surgery for prostate or testicular cancer, melanoma and cancer in the lower abdomen.

• An infection involving the lymphatic vessels — Rarely, a bacterial infection that causes a red stripe on the arm or leg (lymphangitis) can be severe enough to cause lymphedema. In areas of the tropics and subtropics, such as South American, the Caribbean, Africa, Asia and the South Pacific, parasites commonly cause lymphedema. Filariasis, a parasitic worm infection, blocks the lymph channels and causes swelling and thickening below the skin, usually in the legs. Filariasis rarely is seen in the United States, except in people who emigrated from tropical areas.

• Cancer — Lymphoma, a cancer that starts in the lymph nodes, or other types of cancer that spread to the lymph nodes may block lymph vessels.

• Radiation therapy for cancer — This treatment can cause scar tissue to develop and block the lymphatic vessels.

When lymphedema occurs without any known injury or infection, it is called primary lymphedema. Doctors diagnose three types of primary lymphedema according to when symptoms first appear:

At birth — Also known as congenital lymphedema. Risk is higher in female newborns. The legs are affected more often than the arms. Usually both legs are swollen.

After birth but before age 36 — Usually, it is first noted during the early teenage years. This is the most common type of primary lymphedema.

Age 36 and older — This is the rarest type of primary lymphedema.

All three types of primary lymphedema are probably related to the abnormal development of lymph channels before birth. The difference is when in life they first cause swelling of the legs or arms.