Newborn Screening

By Dr Gary Wenick and Dr Eitan Kilchevsky

In the first days of life all newborn infants are screened by a simple heel-prick test.  A newborn infant may look perfectly normal, but still may have an inherited disease.  Diagnosing and, more importantly, early treatment of these disorders, may prevent many serious complications.

Each state has its own laboratory for testing newborns.  The illnesses we are testing for include the following:

PKU is a rare disorder occurring in one of every 18,000 new babies.  The reason for this disease is lack of an enzyme required to digest the dietary protein phenylalanine.  This can result in permanent brain damage if the protein is not removed from the diet.

Branched-chain ketonuria is also called Maple Syrup Urine Disease because of the smell of the urine of affected infants.  This disorder is also due to a deficiency in an enzyme required to break down a food protein.  In the absence of treatment, the results of this disease can be devastating but with early diagnosis and special diet, results are encouraging.

Galactosemia is a disease manifested by an inability to digest a sugar (galactose) present in milk.  It is manifested by poor growth, jaundice, cataracts and mental retardation.  The treatment includes the use of a special diet.

Homocystinuria is a disease caused by a deficiency in a liver enzyme.  It may result in mental retardation, bleeding problems, eye, bone and liver damage.  A diet rich in vitamin B6 and low in methionine is usually sufficient for these babies.

Hypothyroidism occurs in 1 per 4,000 births.  Lack of sufficient production of this hormone by the thyroid gland leads to its low levels.  This slows down growth and development.  Early replacement of the hormone will prevent the serious sequelai associated with the disease.

Sickle cell disease occurs in 1 out of 500 black newborn infants. The hemoglobin (which is present in red blood cells and is responsible for carrying the oxygen) is abnormal and causes the red blood cell to be shaped like a sickle.  Under certain circumstances infarcts may develop in the lungs, bones or brain.  Although not curable, early diagnosis may help in preventing the complications associated with this disease.

Biothinidase deficiency is a defect in the metabolism of the vitamin biothin.  The disease may cause rashes, visual and hearing defects and brain damage.  An appropriate diet helps these patients to achieve adequate health.  Screening for the HIV virus which is associated with AIDS is a relatively new screening test.  The screening is done on the mother during pregnancy or on the baby, if the mother was not tested.

The results of the tests are reported to the pediatricians.  Re-testing is done routinely in some states (including Connecticut) at the age of two weeks.  In other states the test is repeated if the results are questionable.

Newborn screening is simple, quick and valuable.  Although each one of the above diseases is rare, screening for all of them increases the chance that infants afflicted with potentially devastating, but treatable, diseases will be identified on time.

Dr Gary Wenick and Dr Eitan Kilchevsky are associated with Danbury Hospital.