Primary and secondary lymphoedema have different causes.
Primary lymphoedema
Primary lymphoedema is caused by alterations (known as mutations) in genes responsible for the development of the lymphatic system. Mutated genes interfere with the development of the lymphatic system, resulting in the loss of its ability to drain fluid properly.
Due to the genetic nature of primary lymphoedema, the condition usually runs in families. However, not everyone born to a parent with primary lymphoedema will develop the condition.
Primary lymphoedema is more common in females.
Secondary lymphoedema
Secondary lymphoedema can have different causes. The most common are explained below.
Surgical treatment of cancer
Cancer spreads around the body via the lymphatic system and so part of the treatment can involve surgically removing the cancerous lymph nodes. The surgeon will try to ensure the rest of your lymphatic system is still able to operate normally, although this is not always possible.
There is a significant risk of lymphoedema occurring as a complication of treatment for:
- breast cancer
- skin cancer
- gynaecological cancers, such as cervical cancer and vulval cancer
- genitourinary cancers, such as prostate cancer or penile cancer
Radiotherapy
Radiotherapy uses controlled doses of high-energy radiation to destroy cancerous tissue. However, it can also damage healthy tissue. If it is necessary to use radiotherapy to destroy cancerous cells present in your lymph nodes or vessels, there is a risk that the nodes and vessels will become permanently damaged.
Infections
In some cases, an infection can cause lymphoedema.
Cellulitis is a bacterial skin infection that can cause lymphoedema, it is also sometimes a complication of the condition. A severe cellulitis infection can damage the tissue around lymph nodes or vessels, leading to scarring.
Another infectious cause of lymphoedema is a parasite infection called filariasis. This can be common in parts of the developing world, such as parts of India, but is not a risk in the UK.
Inflammation
Conditions that cause tissue to become inflamed (red and swollen) can also permanently damage the lymphatic system. Health conditions that can cause lymphoedema include:
- rheumatoid arthritis – which causes pain and swelling in the joints
- eczema – which causes the skin to become itchy, reddened, dry and cracked
Venous diseases
Venous diseases, which affect the flow of blood through the veins, can cause lymphoedema in some people. The abnormal or damaged veins can result in excess blood or fluid building up in tissues, which causes tissue damage. This can affect the drainage of the lymphatic system.
Some venous diseases that can lead to lymphoedema include:
- deep vein thrombosis (DVT) – a blood clot in one of the deep veins in the body
- varicose veins (swollen and enlarged veins) – where poor drainage of blood in the veins causes higher vein pressure and more fluid passes into the tissues
Trauma and injury
In a small number of cases, lymphoedema can be caused by a general injury or trauma, such as a burn or extensive scarring.
Reduced movement
The movement of the surrounding muscles when you exercise or move helps lymph drainage. Therefore, reduced movement can lead to lymphoedema because the fluid in the lymphatic system does not get moved on, causing swelling.
People who are paralysed may be at risk of developing lymphoedema as a result of being unable to move. Someone who is chair-bound for a long time due to an illness may also be at risk of lymphoedema in their legs because they are not moving.