Can Genetic Testing Identify Endometriosis?

 

A few years ago, the answer to the above question would have been a resounding “No”. The gold standard for diagnosing endometriosis was, and is, laparoscopy. Yet, recent advances in the field of genetics have identified biomarkers in the genome which could help identify women who are at risk of developing endometriosis.

Endometriosis is a debilitating gynaecological disease affecting 5-10% of women of reproductive age and 20-50% of women with infertility.1 With endometrioris, tissues similar to the lining of the uterus (endometrium) grow in other parts of the body, like the ovaries and fallopian tubes, resulting in scar tissue and adhesion in areas of the endometrial implant.

The primary symptom of endometriosis is usually pelvic pain and it is often confused with other conditions which cause pelvic pain like ovarian cysts, or even conditions like irritable bowel syndrome. Endometriosis also results in infertility. Some women are asymptomatic; they do not present any classical symptoms of endometriosis and are first diagnosed when they seek treatment for infertility.

The Endometriosis Foundation of America, at their 4th Annual Medical Symposium in March this year2, focussed on endometriosis care: American Perspective – examining the stand of the health care system on endometriosis treatment and identifying opportunities to make it better.

Questions put forward for discussions during the Symposium included:

How do we get Americans to recognize endometriosis as a disease rather than a condition?

How can we prevent the delay of diagnosis?

How can we prevent ‘hit and miss’ surgeries?

Diagnosing endometriosis can consist of pelvic examination, ultrasound imaging or laparoscopy. A pelvic examination cannot identify small areas of endometriosis while ultrasound imaging does not definitively identify endometriosis, though it can identify cysts associated with endometriosis. On the other hand, laparoscopy, which is done under general anaesthesia, can provide definite information about location, extent and size of the endometrial implant.

However, asymptomatic women might not be willing to undergo an invasive surgical procedure to diagnose a condition she may/may not have, but if a non invasive screening test was available, it would help identify the risk of developing endometriosis and prevent a delay in diagnosis.

Although the heritable component of endometriosis is well known, a genetic test is not yet available. However, the risk of developing endometriosis for first-degree relatives of women with severe endometriosis is six times higher than that for relatives of unaffected women.

Unlike familial breast cancer which is a monogenetic mutational disease (e.g. mutations in one gene BRCA1, can cause breast cancer), endometriosis is a polygenic, multifactorial disease with several genes involved. A relatively new way of identifying disease causing mutations, Genome Wide Association Studies (GWAS), have been used to compare the DNA of thousands of women who have endometriosis with the DNA of women who did not, searching for variations in the DNA or genetic markers which occur more frequently in women with the disease.

GWAS3-5 studies have identified a handful of genetic markers associated with an increased risk of endometriosis. Although each variation or ‘risk allele’ identified increases the probability of a disease by a small fraction, collectively these markers explain a larger proportion of the disease risk. Also, these studies are helping identify genes which might play a role in the etiology of the disease. Scientists and doctors can study these genes to elucidate the molecular mechanisms of endometriosis.

The genes identified are known to impact uterine or embryonic development (WNT4, VEZT), hormonal activity (FH1, GREB1) and the risk of cancer (CDKN2BAS, WNT4, VEZT). A comprehensive analysis of these genes may reveal additional markers that impact fertility.

Today, the genetic knowhow may help with early disease diagnostics and may reduce the need for surgery that is now being used as a diagnostic tool. In the future, this knowledge may translate to more effective treatments for infertility.

 

Author: Gouri Mukerjee

www.geneyouin.ca

 

References:

1.  Eskenazi B, et al. (1997) Epidemiology of endometriosis. Obstet Gynecol Clin North Am  24:235

2.  http://www.endofound.org/medicalconference

3.  Uno S, et al. (2010)  A genome-wide association study identifies genetic variants in the CDKN2BAS locus associated with endometriosis in Japanese. Nat Genet 42:707

4.   Painter JN, et al. (2011) Genome-wide association study identifies a locus at 7p15.2 associated with endometriosis. Nat Genet 43:51

5.  Nyholt DR, et al. (2012) Genome-wide association meta-analysis identifies new endometriosis risk loci. Nat Genet 44:1355