American Medical Association Family Medical Guide - American Medical Association [665]
Turner syndrome can be diagnosed from chromosome analysis that detects the missing X chromosome. If your daughter has coarctation of the aorta or another type of congenital heart defect (see page 389), she may need surgery to correct it. When your child is about 3 to 5 years old, the doctor may recommend growth hormone treatment to increase her final adult height. When she is about 12 or 13, she will begin taking the female sex hormones estrogen and progesterone in pill form to stimulate her sexual development. She must continue taking these hormones until at least the age of menopause (usually at about 50).
Klinefelter Syndrome
Klinefelter syndrome is a chromosome abnormality that affects only males and makes them unable to produce sperm. Klinefelter syndrome results when a boy inherits an extra X chromosome, giving him two X chromosomes and a Y chromosome. The extra X chromosome interferes with the production of the male sex hormone testosterone.
If you have a son with Klinefelter syndrome and you are thinking about having more children, talk to a genetic counselor (see page 952) about your chances of having another child with the disorder. A genetic counselor can also help your son understand his genetic makeup and learn to cope with his infertility.
Symptoms
A boy with Klinefelter syndrome usually appears normal at birth but eventually grows tall and thin, may have a feminine build, and has a small penis and testicles. At puberty he may develop breast tissue that may continue to grow throughout adolescence. Adolescents with Klinefelter syndrome have normal erections and ejaculate normally, but their semen does not contain sperm. They usually have little facial hair. Some boys may have learning problems and a degree of mental retardation.
Diagnosis
Klinefelter syndrome can be diagnosed in a fetus using chromosome analysis. If the disorder has not been detected prenatally or during childhood, a doctor who recognizes the characteristic physical features in a child at puberty will recommend genetic testing. The diagnosis may be made in a younger child if a chromosome analysis is performed to find the cause of learning problems.
Treatment
Treatment for Klinefelter syndrome consists primarily of monitoring the boy’s testosterone level each year, starting at age 12 or 13. If his testosterone level is low, he is given monthly injections of a synthetic form of testosterone to help promote normal physical and sexual development. (The testosterone supplements do not, however, give him the ability to make sperm.) As he gets older, he may need to have more frequent injections. If his breasts become enlarged enough to cause embarrassment, they can be reduced surgically.
Autosomal Recessive Disorders
Many genetic disorders are inherited as recessive disorders. A person with one copy of a recessive disease gene is called a carrier, and is usually unaffected by the gene because he or she has a healthy copy of the gene that overrides the effects of the defective gene. If two carriers of a defective recessive disease gene have children, each of their children has a 25 percent chance of inheriting both defective copies of the gene (one from each parent) and having the disease, a 50 percent chance of inheriting one defective copy and one healthy copy of the gene and being a carrier like his or her parents, and a 25 percent chance of inheriting two healthy copies of the gene and being neither affected nor a carrier. If only one of the parents has a defective copy of a recessive disease gene, all of their children will be healthy (although each has a 50 percent chance of inheriting a copy of the disease gene and being a carrier).
Recessive inheritance
In recessive inheritance, a person needs to inherit two copies of a defective gene to have a disorder—that is, he or she needs to inherit an abnormal recessive gene from each parent. A carrier has one healthy copy of the gene and one defective copy. Carriers are usually not affected because their healthy copy of the gene overrides the effects of the