Chromosomal abnormalities are problems with one of the 23 pairs of chromosomes. These are structures in the body’s cells that hold genes. For each pair of chromosomes, one comes from the mother and the other comes from the father. An abnormality can change the number of chromosomes, their structure, or their makeup.

Here are a few health problems from chromosomal abnormalities:

Down Syndrome

Down syndrome , now known as trisomy 21, is when a child has an extra chromosome.

Physical and mental growth is delayed. Babies often have weak muscles. They tend to have a small head, a broad, flat face with slanting eyes, and a short nose. The tongue is large and ears are small and set low in the head. The hands are short and broad with a single crease across the palm. Most children have a lower than normal IQ.

Most children survive to become adults. They often live until 45 to 55 years of age. Some adults get dementia at an early age.

This problem can be found before birth during an ultrasound. It is confirmed by testing the baby's chromosomes.

Fragile X Syndrome

Fragile X syndrome is caused by problems in DNA on the X chromosome. Mothers pass down the syndrome to their children. It is more common in boys.

Many children have normal IQ levels. They have delayed growth, large ears, and a bulging chin and forehead. Boys have large testes after puberty. The joints may be extra flexible. There may also be signs of autism. Women may have menopause in their mid 30s.

This problem can be found by tests before or after birth.

Klinefelter Syndrome

Klinefelter syndrome is a problem in which male babies are born with an extra X chromosome (XXY). Most boys have normal or slightly low IQ. Many have speech, reading, and language problems. This may lead to problems with social skills and behavior.

Men are often tall with long arms. They do not have much facial hair growth. Their breasts may also be larger than normal. Puberty will happen at the normal time, but the testes stay small. They are infertile.

This problem may be found during puberty. This is when most of the symptoms start. Chromosome tests will be done.

Klinefelter Syndrome
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Turner Syndrome

In Turner syndrome, girls are born with one of the two X chromosomes partly or completely missing.

Many newborns with Turner syndrome have swelling on the backs of their hands and the tops of their feet. Swelling or loose folds of skin are also on the back of the neck. They may also have a webbed neck, a low hairline at the back of the neck, a broad chest with wide-spaced nipples, and poorly grown nails.

Girls do not have menstrual cycles. The breasts, vagina, and labia do not develop. The ovaries do not hold eggs. Girls and women are almost always short. Obesity is common.

Many girls have problems with visual and spatial skills. They also have problems with planning and focus. They struggle with math, but do well with verbal skills. Intellectual disability is not common.

Noonan Syndrome

Noonan syndrome may or may not be inherited. Children with it have normal chromosomal structure. But they have many features that are like Turner syndrome . Both boys and girls can get this. It is caused by a gene change on chromosome 12.

A child may have webbing of the neck, low-set ears, droopy eyelids, short stature, shortened ring fingers, heart and blood vessel problems, and low IQ. Most people are short. Boys may have small testes. In girls, the ovaries may not be active or may stop working. Puberty may be delayed. Infertility is likely.

Triple X

Triple X syndrome is the most common chromosomal problem in women. It happens when there are three X chromosomes instead of two. Women have mild or no problems. Many people may not get diagnosed. Those with symptoms tend to have a slightly lower IQ and problems with verbal skills. They also may have:

  • Tall stature
  • Low muscle tone
  • Seizures
  • Kidney problems

Sometimes the syndrome causes infertility . But some women with triple X syndrome have given birth to healthy children.

Rarely, some babies have been born with four or even five X chromosomes. The more X chromosomes the girl has, the greater the chance of intellectual disability and physical problems.

XYY Syndrome

XYY syndrome is a problem in which a male baby is born with an extra Y chromosome.

Boys tend to be tall and have problems with language. Their IQ is usually slightly lower. Many have learning problems, attention deficit disorder , and minor behavioral problems.

What are the risk factors for chromosomal abnormalities?What are the symptoms of chromosomal abnormalities?What are the treatments for chromosomal abnormalities?Are there screening tests for chromosomal abnormalities?How can I reduce my risk of having a child with chromosomal abnormalities?What questions should I ask my doctor?Where can I get more information about chromosomal abnormalities?


About Turner syndrome. National Genome Research Institute website. Available at: Accessed May 11, 2022.

Chromosome abnormalities fact sheet. National Human Genome Research Institute website. Available at: Accessed May 11, 2022.

Down syndrome. EBSCO DynaMed website. Available at: Accessed May 11, 2022.

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