There have been several questions about the cause and inheritance of primary lymphedema recently and whether the ReidSleeveŽ is an effective treatment for primary lymphedema. Let me answer the easiest part of the questions first. Many patients with primary lymphedema have had significant benefit from use of the ReidSleeveŽ. Infants, young children, teenagers and adults with primary lymphedema have benefited from using the ReidSleeveŽ.
So what is primary lymphedema? Primary lymphedema is an inherited form of lymphedema. Primary lymphedema may present without a specific cause such as trauma, infection or surgery It may occur at any phase of life but it most commonly appears at puberty. In contrast, secondary lymphedema is seen much more often and is due to a specific cause such as surgery, radiation or trauma. In the US, one of the most common causes is axillary dissection as part of the treatment for breast cancer.
There was a report published just a few weeks ago that sheds some light on the cause of primary or hereditary lymphedema (see Ferrell et. al.). The authors of this study evaluated several families where lymphedema presented in an inherited form. From their studies they were able to conclude that hereditary lymphedema presented in an autosomal dominant pattern. This means that the children of parents with lymphedema are at high risk of developing lymphedema if they inherit the abnormal gene. For example, if the mother of a child has lymphedema and the father is normal, the child has essentially a 50% chance of inheriting the defective gene. However, even if the child inherits this gene, it does not mean they will get lymphedema. Even if a child inherits an abnormal gene, this gene may not be fully expressed or symptoms develop only after a certain age or after trauma or another inciting event.
In genetic terms we describe the strength of a gene as penetrance. If all children who inherit the abnormal gene develop the trait, then there is strong penetrance. If only a fraction of children who inherit the abnormal gene actually develop the trait, then the penetrance is reduced or inconsistent or variable. This is the case with the lymphedema gene. While we cannot predict who will get lymphedema, it is clear that not all children who inherit the gene will show evidence of lymphedema. In the case of primary lymphedema, the penetrance appears to be variable. In addition, the age of presentation can also be quite variable.
The genetics of this disorder are just becoming understood and there is some evidence to suggest that the problem may be related to abnormal expression of endothelial growth factor (for a discussion of vascular endothelial growth factor see previous eNews). However, further experimentation and study is required to fully understand this problem and it is likely that additional genes will be identified. Fortunately, serious scientific studies are underway and we will keep you up to date on new developments in the field. Sincerely,
Tony Reid MD Ph.D
Hereditary lymphedema: evidence for linkage and genetic heterogeneity. Ferrell RE, Levinson KL, Esman JH, Kimak MA, Lawrence EC, Barmada MM, Finegold DN Hum Mol Genet 1998 Dec;7(13):2073-8
Lymphedema: classification, diagnosis and therapy. Szuba A, Rockson SG Vasc Med 1998;3(2):145-56