American Medical Association Family Medical Guide - American Medical Association [672]
The most severe, classic form of galactosemia is a recessive genetic disorder, which results when a child inherits two copies of the defective gene, one from each parent. A less severe form of galactosemia, called Duarte galactosemia, results when a child inherits a copy of the gene for the classic form from one parent and a copy of the Duarte gene from the other parent. In Duarte galactosemia, the enzyme is partly active and able to convert some galactose into glucose.
If you have a child with galactosemia, seek genetic counseling (see page 952) to learn your chances of having another child with the disorder.
Symptoms
The symptoms of untreated galactosemia begin to appear shortly after birth when a newborn drinks breast milk or formula. Early symptoms include yellowing of the skin and the whites of the eyes (jaundice; see page 785) and vomiting. The baby may be irritable, have diarrhea, fail to gain weight, and develop severe infections. Without treatment, a child with galactosemia can develop cataracts or mental retardation.
Diagnosis
Both forms of galactosemia can be diagnosed during newborn screening tests (see page 954). Galactosemia can also be diagnosed during pregnancy with chorionic villus sampling, or CVS (see page 511), or amniocentesis (see page 510) if both parents are carriers of the gene. If your child has not been tested and he or she has symptoms of galactosemia, your doctor will order blood and urine tests to diagnose the disorder.
Treatment
The treatment of galactosemia involves excluding all foods from the diet that contain lactose or galactose—including breast milk, dairy products, and most legumes. Even when a child is started on a restrictive diet at birth, the disorder can cause long-term complications, including speech and language problems, delays in developing fine and gross motor skills, and learning disabilities. For unknown reasons, girls with galactosemia usually have premature ovarian failure that results in infertility.
Homocystinuria
Homocystinuria is an autosomal recessive genetic disorder, an inborn error of metabolism that usually results from a deficiency of an enzyme called cystathionine beta synthase. This enzyme enables the body to properly digest an amino acid in food called methionine. Amino acids are the building blocks of proteins and are essential for healthy growth and development. The inability to properly digest methionine leads to buildup of a protein called homocysteine in the blood, which can interfere with a baby’s growth and development.
Many states now test all newborns for homocystinuria. If not diagnosed and treated early in life, more serious symptoms, such as eye abnormalities and mental retardation, can develop by age 3. If you or your partner has a family history of homocystinuria and you are thinking about having children, talk to a genetic counselor about your risk of passing the disorder on to children. Your children are at risk of inheriting the disorder only if both of you carry a copy of the gene for homocystinuria. The disorder can be diagnosed during pregnancy with chorionic villus sampling, or CVS (see page 511), or amniocentesis (see page 510).
Symptoms
Newborns with homocystinuria appear normal, but they may fail to grow or gain weight at the normal rate and they may not achieve the expected developmental milestones (see page 377). By about age 3, more noticeable symptoms develop, including partial dislocation of the lens of the eye and severe nearsightedness. Many children experience progressive mental retardation and some may have seizures. They tend to be thin and unusually tall, with long legs and arms and long, thin fingers and toes. They may have progressive curving of the spine (scoliosis; see page 433), chest abnormalities (such as a breastbone that protrudes or caves in), and loss of bone density (osteoporosis; see page 989) throughout the body.