Geneticists at the University of South Alabama are using a new and more sensitive battery of tests to diagnose a range of major developmental defects, including mental retardation.
USA is the only facility in the region offering these tests, which are the latest in a host of genetic screenings available to patients. The new screenings allow for earlier diagnosis, as well as improved management and counseling.
“Negative test results help doctors rule out things that are not causing a person’s condition, while positive test results bring to a halt the expensive search for a cause and allow for a focus on intervention,” said Dr. Wladimir Wertelecki, professor and chairman of the USA department of medical genetics.Subtelomere analysis using a panel of DNA probes (for mental retardation of unknown cause).
According to the March of Dimes, about 150,000 babies are born each year with birth defects, which are defined as abnormality of structure, function or body chemistry present at birth that causes disability or death. In 60 to 70 percent of birth defect cases, the cause is unknown – underscoring the importance of innovative screenings that provide more detailed information.
Parents whose children have medical abnormalities that cannot be explained can request the new tests at USA. The blood tests can be performed on anyone from a newborn baby to a grandfather and may determine whether the condition runs in the family.
NEW DNA SCREENINGS
These studies can be reassuring to families in two ways. Negative results provide assurance by providing information about future pregnancies. Equally important, positive results from screenings identify family members who are at risk and those who are not at risk.
“One of the new tests—called the subtelomere panel—uses a series of 41 DNA probes that geneticists use to look for very subtle rearrangements near the telomeres (tips) of the whole array of chromosomes,”said Dr. Cathy M. Tuck-Muller, director of the Cytogenetics Laboratory at USA.
Up to 7 percent of patients with mental retardation of unknown cause have some rearrangement involving the subtelomeric regions of chromosomes. Previously, these regions could not be analyzed accurately. The subtelomere panel provides exponentially more detailed information and accuracy.
Another of the new tests offered, the neonatal hypotonia panel, aids in the diagnosis of the hypotonic infant, sometimes termed “floppy baby” syndrome. This syndrome is a difficult condition to accurately diagnose in newborns and is characterized by inadequate tone of the muscles.
One of tests also offers an earlier, more accurate and cost-effective diagnosis of congenital hearing loss, which affects 1 in 1,000 newborns. The test also can provide information on the chance of recurrence in future pregnancies.
Wertelecki said there has been a good deal of advancement in categorizing and knowing the causes of developmental defects. The first step was a chromosome test, which later was enhanced by painting the chromosome. Then DNA markers were added, but geneticists didn't know to what genes they would adhere. The new tests now identify very specific genes.
“Using the analogy of a telescope to describe the changes in genetic technology, it is if we started with a zoom lens of a magnification of 20 with the chromosome test, then advanced to 50 power by painting the chromosome. These new tools place us in the 200 magnification range and allow us to advance patient care with more precise and detailed information,” Wertelecki said.
The new tests are for patient concerns about unexplained birth defects: neonatal hypotonia; developmental delay; spinal muscular atrophy; mental retardation; non-syndromic deafness; dysmorphisms; infertility; growth disturbances and recurrent pregnancy losses.
The new tests USA is now providing are as follows:
Neonatal hypotonia DNA analysis panel (early diagnosis of Prader-Willi and Angelman syndromes, Spinal Muscular Atrophy and Myotonic Dystrophy).
Enhanced Fragile-X premutation and mutation detection (children with developmental delay and their relatives).
Connexin 26 and 30 mutation analysis (non-syndromic deafness).
Enhanced paternity panel.
Geneticists involved in the new testing at USA include Wertelecki; Tuck-Muller; Dr. T.J. Chen, director of the Molecular Diagnostics Laboratory at USA; and Dr. Jose E. Martinez, professor and clinical geneticist at USA.
The USA Birth Defects Genetics Center provides unique medical services in our region, including prenatal diagnosis, complete and comprehensive genetic clinical and laboratory services and genetic counseling.
For more information about the new tests, call (800) 624-1865 or (251) 460-7500, or visit