primary lymphedema (MONDO_0019175) is a congenital condition that results in swelling in the arms or legs, and can occur during adolescence or adulthood. Loss of motion and pain may also accompany the swelling. Protein-rich lymphatic fluid accumulates in tissues, engorging and enlarging vessels and often causing visible swelling, tenderness, and pain. Left untreated, the affected tissues may continue to swell, and can become hardened or fibrotic and susceptible to infection. Also known as: Troncular lymphatic malformation.