What are chromosomal abnormalities?

Changes in the number or structural abnormalities of chromosomes caused by factors such as medication, infection, or age are referred to as chromosomal abnormalities^[1].

Which department should be consulted for chromosomal abnormalities?

Obstetrics, Reproductive Medicine, Endocrinology

What types are commonly included in chromosomal abnormalities?

• Structural abnormalities: Caused by fragment loss or breakage, etc.^[1].
• Numerical abnormalities: Caused by an increase or decrease in chromosome number^[1].

What are the common causes of chromosomal abnormalities?

The exact causes of chromosomal abnormalities are unclear but may be related to genetics, medication, age, viral infections, and other factors.

• Genetic factors: If one or both parents have chromosomal abnormalities, their child is highly likely to inherit them.
• Medication factors: Certain drugs taken during pregnancy, such as anticancer drugs (e.g., methotrexate), antiepileptics (e.g., phenytoin), antivirals (e.g., vidarabine), or radiopharmaceuticals (e.g., ioversol), may cause chromosomal abnormalities in the embryo.
• Radiation exposure: Exposure to radiation (especially within the first three months of pregnancy) increases the risk of fetal chromosomal abnormalities.
• Age factors: Pregnant women over 35 years old have a higher risk of having a child with chromosomal abnormalities^[1].
• Food additives: Improper use of certain chemical additives, such as cyclamate, may cause chromosomal deformities.
• Chemicals, pesticides, herbicides: Long-term exposure to substances like benzene, toluene, or organophosphate pesticides may lead to chromosomal abnormalities.
• Biological factors: Viral infections (e.g., hepatitis B) or consuming moldy food (which may contain aflatoxin) can also cause chromosomal abnormalities^[1].

Who is at higher risk of chromosomal abnormalities?

• Family history of chromosomal abnormalities: Individuals with affected parents have a higher likelihood of chromosomal abnormalities.
• Long-term exposure to industrial toxins, herbicides, or pesticides: These individuals are more prone to chromosomal abnormalities.
• Advanced maternal age pregnancies: Fetuses of older mothers are more susceptible to chromosomal abnormalities.
• Occupational radiation workers: Frequent exposure to radiation increases the risk.

What are the main manifestations of chromosomal abnormalities?

Chromosomal abnormalities are associated with various diseases. Below are specific manifestations of Down syndrome:

• Facial abnormalities: Flat facial expression, wide-set eyes, upward-slanting palpebral fissures, frequently open mouth with protruding tongue, excessive drooling, small and round head, short and broad neck, low nasal bridge, and small ears.
• Intellectual disabilities: Significant cognitive delays compared to peers, worsening with age, and impaired abstract thinking.
• Physical growth abnormalities: Short stature, low weight, delayed tooth eruption, short and broad fingers with inward curvature, protruding abdomen, and umbilical hernia.
• Other abnormalities: Most adult males are infertile; females may lack menstruation, with only a few retaining fertility. Some children have a single transverse palmar crease.

How are chromosomal abnormalities diagnosed?

Doctors assess based on family history and the following diagnostic methods:

• Physical examination: Evaluates head circumference, nasal bridge height, ear position, eye spacing, and facial symmetry for abnormalities.
• Prenatal screening: Includes ultrasound, estriol level testing, maternal alpha-fetoprotein (AFP), and free β-hCG in the second trimester.
• Karyotype analysis: Compares the patient's chromosomes with a normal karyotype to detect abnormalities.
• Biochemical tests: Assess blood glucose, electrolytes, and urinary metabolites for abnormalities.

How are chromosomal abnormalities treated?

There is currently no cure for chromosomal abnormalities. Treatment focuses on symptom management, prenatal genetic screening, early detection, and, if necessary, pregnancy termination^[2].
Symptomatic treatment: Growth hormone injections may be used for short stature, though efficacy remains uncertain^[1].

How do chromosomal abnormalities affect life?

• Chromosomal additions, deletions, or translocations may impair fertility.
• Conditions like Down syndrome cause intellectual disability and reduced self-care ability.
• Cognitive impairments often hinder employment, education, marriage, and daily living skills.

How can chromosomal abnormalities be prevented?

• Genetic counseling: Avoid consanguineous marriages and seek prenatal genetic advice for hereditary risks.
• Optimal maternal age: Older pregnancies carry higher risks; choose an appropriate age for childbearing.
• Avoid teratogens: Pregnant women should minimize exposure to radiation and harmful drugs.
• Dietary caution: Limit intake of foods with excessive additives during pregnancy.