Causes

There are two types of lymphoedema primary and secondary lymphoedemawhich have different causes.

The main causes of each type of lymphoedema are outlined below.

Primary lymphoedema

Primary lymphoedema is caused by alterations (mutations) in genes responsible for the development of the lymphatic system.

The "faulty" genes cause the parts of the lymphatic system responsible for draining fluid to not develop properly or not work as they should.

Primary lymphoedema often runs in families, although not every child born to someone with the condition will develop it themselves.

Secondary lymphoedema

Secondary lymphoedema develops in people who previously had a normal lymphatic systemthat then becomes damaged.

It can have a number of different causes. Some of the most common causes are explained below.

Surgery for cancer

Treatment for Predictive genetic test for cancer risk genes can involve surgery to remove sections of the lymphatic system.

The surgeon will try to limit damage to your lymphatic system, although this isn't always possible. There's a particular risk of lymphoedema occurringafter treatment forany cancer where lymph glands are removed.

Some of the more common cancers where this happens are:

• breast cancer
• melanoma skin cancer
• gynaecological cancerssuch as cervical cancer and vulval cancer
• genitourinary cancerssuchas prostate cancer or penile cancer

Radiotherapy

Radiotherapy uses controlled doses of high-energy radiation to destroy cancerous tissue, but it can also damage healthy tissue.

If radiotherapy is needed to destroy cancerous cells in your lymphatic system, there's a risk that the lymphatic system could become permanently damaged and unable to drain fluid properly.

Infections

An infection, such as cellulitis , can sometimes cause lymphoedema. Severe cellulitis can damage the tissue around the lymphatic system, causing it to become scarred.

Filariasis is another infectious cause of lymphoedema. Lymphatic filariasis is a parasitic disease caused by microscopic, thread-like worms.

The adult worms only live in the human lymphatic system and block lymph drainage. It's a common cause of lymphoedema worldwide, but it isn't generally a risk in the UK.

Inflammation

Medical conditions that cause tissue to become red and swollen can also permanently damage the lymphatic system.

Conditions that can cause lymphoedema include:

• rheumatoid arthritis causes pain and swelling in the joints
• eczema causes the skin to become itchy, reddened, dry and cracked

Venous diseases

Diseases that affect the flow of blood through the veins can cause lymphoedema in some people.

The abnormal or damaged veins can cause fluid to overflow from the veins into the tissue spaces. This overwhelms and eventually exhausts the parts of the lymphatic system responsible for draining this fluid.

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
• swollen and enlarged veins (varicose veins) where poor drainage of blood in the veins causes higher vein pressure and more fluid overflowing into the surrounding tissues

Obesity

Obesity is another possible cause of secondary lymphoedema. People who are obese, particularly those who are severely obese, have an increased risk of developing swollen body parts.

It's not clear exactly why this is, but it's been suggested that the extra fatty tissue affects the lymphatic channels in some way, reducing the flow of fluid through them.

In these cases, weight loss is an important part of treatment and even just starting to lose weight can make a big difference to the swelling.

Trauma and injury

In a small number of cases, lymphoedema can be caused by an accidental injury to the lymphatic system.

For example, it can sometimes occur after a road traffic accident where there's extensive bruising or soft tissue loss.

Immobility

Movement and exercise help lymph drainage because muscle activity surrounding the lymphatic vessels massages fluid into and along them.

Reduced movement can therefore lead to lymphoedema because the fluid in the lymphatic system doesn't get moved along.

For example, people who have limited mobility for a long period of time as a resultofan illness, nerve damageor arthritis may be at risk of lymphoedema.