American Medical Association Family Medical Guide - American Medical Association [679]
The physical features of fragile X—which are often unnoticeable and are not a health problem—can include large ears, a long face, crossed or wandering eyes, a prominent jaw and forehead, enlarged testicles, and loose joints. The features are usually more subtle in girls.
Diagnosis
If your child is not developing at the normal rate or if your doctor knows that you or your partner has a family history of fragile X syndrome, he or she will order a blood test to look for the defective gene. For prospective parents who have a family history of fragile X syndrome, a diagnosis of fragile X in the fetus can be made during pregnancy with chorionic villus sampling, or CVS (see page 511), or amniocentesis (see page 510).
Treatment
Fragile X syndrome has no specific treatment. Your doctor may prescribe medication for your child to treat behavior problems, which are common in boys with fragile X. Make sure that your child has access to special education services and interventions available in your community to help him or her reach his or her full potential.
Muscular Dystrophy
Muscular dystrophy is a group of inherited genetic disorders that cause muscle weakness that worsens over time. A person’s muscles waste away as muscle cells die and are replaced by fat and connective tissue. Although there are nine different types of muscular dystrophy, the two most common are Duchenne muscular dystrophy and Becker muscular dystrophy. They are the same disease, except that Duchenne muscular dystrophy develops at an earlier age and progresses more rapidly. Some of the other forms of muscular dystrophy may not produce symptoms until adulthood. Because the disorder is carried on the X chromosome, boys are more likely to be affected than girls.
Symptoms
The symptoms of muscular dystrophy usually are not apparent until about age 3, although infants may have slow development and muscle weakness. The child begins to lose strength in his or her legs and hips from the gradual wasting away of muscle and may walk with feet wide apart to maintain balance. He or she may have trouble climbing stairs. Frequent falls and difficulty getting up or standing up straight are common. The calf muscles often look larger than normal because fat and connective tissue have replaced muscle. By age 10, a child may need braces for walking and, by age 12, may require a wheelchair.
The disease progresses to the muscles in the arms, neck, and upper half of the body, causing the bones in the chest and spine to develop abnormally. The bone deformities combined with the muscle weakness can make breathing difficult and can interfere with the functioning of the heart. Some children have mental impairment. Children with Duchenne muscular dystrophy usually die of pneumonia (see page 660) or other lung problems by late adolescence. Becker muscular dystrophy produces similar symptoms but they don’t appear until about age 7 and progress slowly. However, Becker muscular dystrophy is usually fatal by age 40.
If you have a child with muscular dystrophy, you and other members of your family would benefit from genetic counseling (see page 952) to learn your risks of transmitting the gene to future children.
Leg muscle weakness in muscular dystrophy
Because muscular dystrophy causes muscle weakness in the legs, a child with muscular dystrophy uses his or her arms and hands to get up to a standing position from sitting on the floor.
Diagnosis
If a child has symptoms of muscular dystrophy, the doctor will order a blood test that can detect levels of specific proteins in the blood. He or she may also order a test called electromyography, which evaluates the electrical activity in muscles. To confirm the diagnosis, the doctor may recommend a biopsy (in which a sample of the child’s muscle tissue is sent to a laboratory for examination) or genetic testing of a sample of the child’s blood.