Metabolic disorders take the life of one baby in every 4,500.
Metabolic disorders take the life of one baby in every 4,500.
About 24 hours after birth, a nurse takes a small blood sample from each infant . The blood is dropped onto a piece of filter paper and sent to the Department of Health, Newborn Screening Program laboratory. The presence of district chemical signatures in the blood sample are a warning signal to doctors and parents that the infant may have one of four debilitating genetic disorders.
None of these disorders are common or curable. However, strict dietary and medical precautions can prevent developmental retardation and fatalities in the affected children. But there are still many other disorders newborns aren’t tested for. Should the additional tests be added?
Melanie and Dell Ruff definitively believe so. They nearly lost their daughter, Anna Katherine, to a rare but treatable genetic disorder.
Anna Katherine was an active, healthy and happy 17-month-old when she became ill with a common stomach virus. Anna Katherine’s reaction was far from normal. She began with the normal stomach flu symptoms – lack of appetite, vomiting and diarrhea. But after a day and a half, Anna Katherine became lethargic and unresponsive. After consulting with her doctor, Anna Katherine was rushed to the emergency room.
In the hospital, a blood sugar test showed that Anna Katherine had abnormally low blood sugar. Intravenous glucose saved her life. The doctors at the hospital were unable to explain her symptoms. One week later, after an array of blood tests, Anna Katherine was diagnosed with MCAD (Medium Chain Acyl CoA Dehydrogenase Deficiency). People with MCAD cannot convert stored fat to blood sugar. As Anna Katherine’s body ran out of blood sugar, she was unable to access her body’s natural energy reserve and her blood sugar dropped to critical levels.
During the past decade, screening tests for MCAD, and more than 30 similar genetic disorders, were developed. The new tests are done with a technique called Tandem Mass Spectrometry at three laboratories in the United States. For the infant, the test is no different from that currently performed – a small pinprick to the heel. Blood is dropped onto a filter paper postcard and sent to the laboratory. The laboratory cost of the test is usually less than $25.
These disorders are all rare; most occur in fewer than one in 60,000 children with a combined incidence of about one child in 4,500. Some of the disorders occur most frequently in specific genetic groups. For example, sickle cell disease is most common to people of African or Mediterranean heritage, and maple syrup urine disorder is most common in Mennonite populations.
Only a few states have made comprehensive newborn screening mandatory. To date, the legislature has decided that the additional cost of testing is not warranted by the incidence of these diseases. But if only one baby were spared …
Cheryl Major, R.N.C., B.S.N., outreach coordinator for Vanderbilt University’s Division of Neonatology, points out that tests are not as simple as they first appear. Nurses must be trained to collect the blood in a specific manner. Too much, too little or multiple drops of blood spoil the sample.
Testing difficulties are increased at hospitals that treat large numbers of sick or premature infants. Because the tests look for waste products of the digestive process, the blood sample must be collected after the child has begun feeding. However, for other disorders, the sampling must occur before transfusion. Meeting these criteria can be impossible in sick babies and a return visit to the hospital is required to meet state regulations.
A Matter of Ethics
New ethical considerations arise as our understanding of the genetic causes of disease increases. It is possible to test for diseases for which there is no treatment. Do we want this information? Do we want doctors, insurance companies or the government to have access to our genetic information? Technology is currently outpacing the societal ethics and some argue that we should refrain from comprehensive testing until ethical and legal considerations have been addressed.
Because mandatory comprehensive testing is unlikely in the immediate future, parents who have special concerns should talk with their pediatrician. Because the disorders are genetic, a family history of unexplained infant deaths or developmental retardation may be indications that additional testing should be done. Unfortunately, because these are recessive disorders, there may be no indication that a family carries the faulty genes.
Newborn Screening Program
PKU is a congenital metabolic impairment. Children with PKU are unable to digest the amino acid phenylalanine. There are no symptoms in early infancy. Developmental retardation symptoms are observed between 6 and 12 months of age. This disorder can be treated with strict dietary restriction of phenylalanine. Special formulas and food are required throughout childhood and adolescence.
Galactosemia is an inherited metabolic disorder that is usually fatal. Children with this disorder cannot convert milk sugar (galactose) to usable glucose, and their bodies therefore cannot develop normally. Treatment requires a lactose-free diet. For good results, treatment for the disorder must begin within 10 days of birth.
Hypothyroidism results from decreased thyroid function. Symptoms may not appear until the infant is several months old. Children with this disorder may have mental retardation, growth failure and deafness, among other symptoms. If treatment with synthetic thyroid hormones is begun within a month of birth, children generally develop normally.
Hemoglobinopathies are a class of genetic disorders that affect the kind and amount of red blood cells. Sickle cell disease occurs most commonly in people of African or Mediterranean heritage. These diseases can be fatal and result in a variety of physical problems. Treatment usually entails fluid therapy, analgesics and transfusion.
Congenital Adrenal Hyperplasia
In the year 2000, the state will begin testing for congenital adrenal hyperplasia. This disorder is the result of defects in the natural production of sexual hormones and can cause ambiguous genitalia in girls. It also impacts the uptake and retention of salt; the inability to retain salt can be fatal to newborns. Treatment is complicated but available.
Lisa Wells is a mother and freelance writer.