Primary lymphoedema occurs when the lymphatic vessels or lymph nodes have not completely developed or have developed abnormally before birth. The swelling may be present at birth or present later on in life.
Secondary lymphoedema occurs as a result of damage to or obstruction of the normal lymphatic system, resulting in an inability of the lymphatic system to transport lymph back into the circulatory system. This is most commonly due to surgery in the axilla (armpit) or groin to remove lymph nodes usually for cancer treatment and is most commonly a complication of breast cancer and gynaecological cancers. Radiotherapy may also complicate with lymphoedema. Other causes of secondary lymphoedema include trauma or surgery, venous insufficiency, a blood clot (post-thrombotic syndrome), obesity, untreated wounds or infections amongst others.