Definition of Lymphedema

Lymphedema: A common chronic, debilitating condition in which excess fluid called lymph collects in tissues and causes swelling (edema) in them.

Lymphedema (edema due to lymphatic fluid) may occur in the arms or legs. This often happens after lymph vessels or lymph nodes in the axilla (armpit) or groin are removed by surgery or damaged by radiation, impairing the normal drainage of lymphatic fluid. Lymphedema may also due to a mass such as a tumor pressing on the lymphatic vessels.

Congenital lymphedema: In many other cases, lymphedema is evident at birth and is due to a congenital malformation (that is, a birth defect) of the lymphatic system. Congenital lymphedema can be found associated with the Noonan and Turner syndromes and a number of forms of lymphedema are clearly due to genetic factors.

Genetic factors in lymphedema: Hereditary lymphedema is heterogeneous and usually occurs as an autosomal dominant trait. The most common form of congenital primary hereditary lymphedema is Milroy disease which is sometimes caused by mutations (changes) in the vascular endothelial growth factor receptor-3 gene (VEGFR-3, or FLT4)

The lymphedema-distichiasis (LD) syndrome is a less common cause of hereditary lymphedema. In LD there is lymphedema (primarily of the limbs, with variable age at onset) together with distichiasis, (double rows of eyelashes). There may also be heart defects, cleft palate, extradural cysts, and photophobia. A gene for LD was mapped by linkage studies to chromosome band 16q24.3. In families with LD, mutations have been found in the FOXC2 (MFH-1) gene. FOXC2 is a member of the forkhead/winged-helix family of transcription factors, whose members are involved in diverse developmental pathways. (Fang et al. Am J Hum Genet 67:1382-1388, 2000)