Primary and secondary lymphedema are the two main types of lymphedema. In both cases, missing or damaged lymph vessels or lymph nodes cause a blockage of the lymphatic system. The protein-rich fluid called lymph or lymphatic fluid is unable to drain properly and collects in the tissues. This results in swelling in the affected areas.
Causes of primary lymphedema
Primary lymphedema is a rare disease that occurs when the lymphatic system has not developed adequately (or is not functioning as it should) from birth due to a genetic reason. Primary lymphedema develops as soon as the lymph vessel system can no longer cope with the strain. This usually happens in early life. It is called 'primary' because the impairment is not due to a ‘secondary’ cause like an illness or an injury.
Primary lymphedema can have different causes:
- Aplasia: Parts of the lymphatic system are missing.
- Hypoplasia: Lymphatic vessels are underdeveloped or present in below-average numbers. This is the most common cause of primary lymphedema.
- Hyperplasia: Lymphatic vessels are larger than normal and don't work as well as normal-sized vessels.
- Fibrosis of lymph nodes: hardening and scarring of the tissue
There are different types of primary lymphedema and there are many known syndromes that have been linked with it, including Noonan Syndrome, Prader Willi, Yellow Nail Syndrome, and Turner Syndrome.
An example for the congenital onset lymphedema is Milroy’s disease where the lymphedema is noticed at birth or shortly afterwards. The late onset primary lymphedema (e.g. Meige disease) presents at a later stage, with Meige disease usually around puberty.
Causes of secondary lymphedema
Secondary lymphedema is more common than primary lymphedema and is caused by another disease or an injury. The lymphedema develops either because the lymphatic system is damaged or there is too much lymph fluid that cannot be drained properly (overload).
Damages to the lymphatic system can be a result of:
- Complications from cancer treatment: Lymphedema can develop after cancer treatment, such as the removal of lymph nodes after surgery, radiation treatment or after some types of chemotherapy or hormone treatment. Lymphedema is most commonly seen with breast cancer in women and with prostate cancer in men. Other cancer types that are often associated with lymphedema are:
- Cancer in the pelvic area: bladder, testicles, penis, cervix, ovaries, vulva, or rectum.
- Lymphoma: cancer that affects specific cells of your immune system.
- Melanoma: skin cancer with a high risk to grow and spread.
- Cancer in the area of the head and neck.
- Wound or skin infections, such as cellulitis, especially in case of repeated infections.
- Trauma: e.g., severe crushing, burning, scarring, large wounds.
- Filariasis: This is a parasitic disease found mostly in African and in some Asian countries. It is caused by roundworms that infiltrate the lymphatic system and block the lymphatic flow. The parasites are spread by mosquitoes or black flies.
An overload of the lymphatic system can be a result of:
- Obesity: overweight can add additional stress to the lymphatic system putting pressure onto lymph nodes and vessels.
- Reduced or limited movement: for example paralysis or muscle weakness following a stroke.
- Chronic venous disease; for example varicose veins or following a deep vein thrombosis (DVT).
- Chronic skin disorders such as eczema or psoriasis.
- Tumor regression: localized or advancing tumors may block the local Lymphatic Drainage.
- Inflammatory diseases, such as rheumatoid arthritis.
All these causes affect the lymphatic system. They either impair the flow, increase higher lymph production, damage the lymph vessels or cause pressure on the lymphatic system.