Milroy's disease, also known as primary lymphedema type II, is a rare genetic disorder characterized by the abnormal development of the lymphatic system. This condition leads to the buildup of lymph fluid in tissues, resulting in swelling, particularly in the limbs. While often referred to as "Milroy disease", it is essential to note that this condition has various synonyms, including Milroy's primary lymphedema, congenital lymphedema, hereditary lymphedema, and hereditary marked lymphedema. These terms can be used interchangeably to describe the same medical condition. It is crucial for individuals affected by this disorder or those seeking information to be aware of these interchangeable terms.