The visceral manifestations of lymphatic disorders (lymphangiomatosis and lymphangiectasia) are particularly severe. Any pathology of the lymphatic vasculature, whether superficial or internal, regional, or systemic, is predominated by the appearance of lymphedema, the characteristic form of tissue edema that occurs when lymphatic dysfunction supervenes. Disease manifestations may include dysregulation of body fluid homeostasis, immune traffic impairment, and disturbances of lipid and protein reabsorption from the gut lumen. The appearance of lymphatic edema invokes complex biological alterations. Many of these changes seem to relate uniquely to chronic lymphatic edema, including a profound stimulus to collagen and adipose deposition. Despite the recent advances in our understanding of these disorders, substantial knowledge gaps remain; these gaps inhibit our ability to accurately identify, categorize, treat, and prevent these diseases. Future diagnostic, therapeutic, and reproductive decisions for affected individuals require an accurate knowledge of the clinical and laboratory presentation, mode of inheritance, treatment response, outcomes, and prognosis.