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Chromosome diseases are abnormalities that develop when there are errors on one or more of a person’s chromosomes. Such errors may include broken pieces, missing chromosomes, or extra chromosomes. Cells of the human body normally have 46 chromosomes or 23 pairs. Sex cells, which are referred to as gametes, normally have 23 chromosomes. Among the most common types of chromosome diseases are Down syndrome, trisomy 18, Turner syndrome, and Klinefelter syndrome.
Down syndrome is a common type of chromosome disease. According to the March of Dimes, approximately one out of every 800 babies is born with Down syndrome. The number of fetuses affected may be higher than this, however, as many babies with this and other chromosomal abnormalities do not survive until birth.
People born with Down syndrome have an additional copy of chromosome 21. This means there are three copies of chromosome 21 instead of the normal chromosomal pair. A person with this chromosome disease may have small hands and feet, upward slanting eyes, and poor muscle tone. Mental retardation is another symptom of Down syndrome, as is a shortened life span. Many people with Down syndrome also experience a range of health problems, including those that affect the heart.
Trisomy 18 is a chromosome disease caused by an extra copy of chromosome 18. A person with this condition may have heart and kidney defects, digestive tract abnormalities, and a range of appearance abnormalities, such as delayed growth, a small head, small jaws, and low-set ears. Trisomy 18 is also marked by serious developmental delays and high mortality rates.
Turner syndrome is a chromosome disorder that only affects females. It develops when a female child only has one X chromosome instead of the two that are normal for female children. When a child is born with this condition, she may be shorter than most girls, and her ovaries may not function properly. This means she may be infertile as an adult woman.
A person with Turner syndrome may also have hearing, kidney, heart, and thyroid problems. She would, however, typically have normal intelligence, though she may struggle with learning some subjects, such as math. Girls with this condition may need hormone treatment to begin puberty.
Klinefelter syndrome is a chromosome disease that affects males. Instead of having an XY pattern in their cells, which is normal for boy children, people with Klinefelter syndrome have an extra X chromosome. This results in an XXY pattern.
Males with this condition tend to be taller and have less muscular strength and impaired coordination. During puberty, they may have less hair on the face and body than other boys their age. Some boys with this condition develop broader hips and more noticeable breast tissue. Their bones tend to be weaker as well.
People with Klinefelter syndrome may have speech delays, reading difficulties, and problems understanding what they hear. During the childhood and teen years, these males may have more trouble fitting in with others, often because of lacking self-confidence and learning difficulties. They tend to have normal social relationships as adults, however.
Though some people may refer to chromosomal abnormalities as diseases, they are not contagious. People are simply born with them. Unfortunately, they are not curable. Still, there are many treatments for the health and developmental symptoms common in those with chromosome abnormalities.