Hereditary lymphedema III is a form of generalized lymphatic dysplasia (GLD), which is characterized by a uniform, widespread lymphedema affecting all segments of the body, with systemic involvement such as intestinal and/or pulmonary lymphangiectasia, pleural effusions, chylothoraces and/or pericardial effusions. In LMPH3, there is a high incidence of nonimmune hydrops fetalis (NIHF) with either death or complete resolution of the neonatal edema but childhood onset of lymphedema with or without systemic involvement. Mild facial edema is often present. Patients have normal intelligence and no seizures (summary by Fotiou et al., 2015). The disease is Experimental Factor Ontology term EFO_0009153 (lymphedema, hereditary, iii). Also known as: LMPH3, Lymphedema, Hereditary, type III.