Cystic Hygromas are non-malignant malformations of lymphatic vessels, usually occurring around the head and neck region. They are usually evident by 3 years of age. They may be single or multiple. If they are large they may be detected on antenatal ultrasound scans. They are usually slow-growing and may spontaneously resolve or reduce in size. Rapid growth does occasionally occur if there is internal bleeding into the cysts or if there is a complicating infection.

Large cysts present at birth may necessitate a tracheostomy if there is pressure on the airway, though this is rare. Small cysts may not require any specific treatment except to wait and see how they develop. Larger cysts which continue to grow may need to be actively treated. Laser treatment to cystic hygromas in the mouth can help to reduce their bulk to help eating. Surgical reduction of these lesions in either the mouth or neck may also be helpful. An alternative treatment has been to use an attenuated bacteria (OK432) as an injection into the cysts, which causes a local sclerosing reaction which may help to reduce the size of the lesions.

Inheritance patterns
No hereditary association has been identified

Pre-natal diagnosis
In some cases the condition has been diagnosed through ultrasound scanning while in others it has remained undetected. This is because there is a wide variation in the extent of the condition which ranges from a small growth on the neck to a very extensive mass of growths.