By R. Ian Hardy, M.D., Ph.D., Board-Certified Reproductive Endocrinologist, Medical Director
Hurler syndrome … Usher syndrome … Krabbe disease … Smith-Lemli-Opitz (SLO) syndrome … you’ve probably never heard of these genetic syndromes? For most infertility couples, these rare genetic diseases would not be their first thought in the infertility evaluation process. However, the first step in achieving a child – - conception – - is ultimately the combination of two separate gene pools. Within these gene pools may be rare genetic disorders that potentially can be passed on to your child and affect your child’s health and well-being. The individual incidence of many of these genetic disorders is so rare that routine testing was not practical. SLO syndrome, for example, has an incidence of 1 in 60,000. Collectively, however, there are hundreds of single gene disorders. When combining over 100 of these disorders, the collective incidence of having one of these many disorders becomes more common. In fact, on average, each person is estimated to be a carrier of approximately four recessive mutations.
If you carry one of these autosomal recessive genetic mutations, what does this mean for your child? In autosomal recessivediseases, both mom and dad need to be carriers of the disease to pass the disease on to their child. In cases where both mom and dad are carriers, the child has a 25% (1 in 4) risk of acquiring the disease. As it turns out, the odds for both mom and dad being carriers of a rare genetic disease is very low. This low risk combined with the prohibitive screening costs historically prevented routine screening for the 100+ autosomal recessive gene disorders. It has been calculated that prior screening techniques would cost over $100,000 to screen for the 100+ gene disorders.
Although rare, single gene disorders have been estimated to account for 10% of pediatric deaths. The vast majority of affected children had no known family history of the genetic disorder. Each year in America, approximately 8000 babies are born with sickle cell disease and more than 2,000 babies are born with cystic fibrosis; worldwide, more than 400,000 infants are born with thalassemia annually.
Recent advances in DNA microarray chip technology have enabled a 600-fold decrease in screening cost, thus enabling a more thorough genetic screening. The Fertility Centers of New England is now offering universal genetic testing for all new patients as part of their standard evaluation. This genetic test, performed by Counsyl (www.counsyl.com) and covered by most insurances, screens for over 100 single gene disorders. These disorders include cystic fibrosis, Tay-Sachs, sickle cell disease and beta thalassemia. A full list of diseases screened with universal genetic testing can be found at https://early.counsyl.com/diseases/ .
Typically, only the female patient is initially screened. A saliva specimen collecting kit will be mailed to your home; the collected saliva specimen is then mailed to Counsyl. If a female patient is shown to be a carrier of an autosomal recessive disease, only then would her male partner be screened. Only if both mom and dad were shown to be carriers of the same disease would further treatment be required. In cases where both partners are carriers of the same disease, preimplantation genetic diagnosis (PGD) is recommended. Further information on PGD can be found on our website (http://www.fertilitycenter.com/assets/pdf/fnce_pgd.pdf ).
