The lymphatic system is a network of lymphoid organs and lymphatic vessels and is the body’s drain. Lymphatic disorders, such as lymphoedema and lymphatic malformations, result from a failure of the lymphatic system to transport fluid and immune cells from the body’s tissues for recycling. The discovery of genetic causes has changed the way we approach diagnosis and management. Knowing the genetic cause enables better understanding of natural history, associated conditions, inheritance patterns and how these disorders develop. An updated algorithm is presented to help improve the clinical approach and make a correct, and possibly genetic, diagnosis. (By Professor Sahar Mansour, https://jmg.bmj.com/content/early/2020/05/14/jmedgenet-2019-106084 )