Trisomy 18 syndrome

What is Trisomy 18 syndrome?

Also known as Edwards syndrome, it is a rare chromosomal syndrome that presents with anomalies and symptoms that affect many parts of the body. Due to the severity of symptoms, many infants with the condition die before birth or in the first month of life. The 5-10% of children who survive the first year have severe intellectual disability. The risk of having a child with Trisomy 18 syndrome increases with the age of the mother.

This syndrome is also known as:
Edward’s syndrome

What gene changes cause Trisomy 18 syndrome?

The syndrome is caused by the presence of three copies of chromosome 18 in each cell rather than two. In the 5% of people with an extra chromosome 18 in just some of the cells of the body they have a form of the condition known as mosaic trisomy 18.

The majority of cases occur as the result of random events during the reproductive process. It is usually not inherited.

What are the main symptoms of Trisomy 18 syndrome?

  • The main symptoms of the syndrome include slow growth before birth with a subsequent low birth weight.
  • Physical features of the syndrome include a small head, an abnormally shaped head, a small jaw and mouth, and fists that are clenched with overlapping fingers.
  • Congenital heart defects and organ abnormalities are common and are usually diagnosed before birth. These serious medical conditions contribute to the short life expectancy of infants with the syndrome, many of whom do not survive birth.
  • In the small number of infants with the syndrome who survive the first year, intellectual disability is a major symptom of the condition.

Possible clinical traits/features:
Abnormality of dental enamel, Enthesitis, Elevated alkaline phosphatase, Elevated circulating parathyroid hormone level, Craniofacial hyperostosis, Femoral bowing, Fibular bowing, Renal phosphate wasting, Phenotypic variability, Spinal canal stenosis, X-linked dominant inheritance, Trapezoidal distal femoral condyles, Premature loss of teeth, Hypophosphatemic rickets, Shortening of the talar neck, Tibial bowing, Recurrent fractures, Spinal cord compression, Frontal bossing, Abnormal concentration of calcium in blood, Abnormality of the metaphysis, Abnormality of pelvic girdle bone morphology, Bowing of the legs, Bone pain, Arthralgia, Renal tubular dysfunction, Osteoarthritis, Osteomalacia, Hearing impairment, Short stature, Genu varum, Flattening of the talar dome, Metaphyseal irregularity, Hypophosphatemia, Hypomineralization of enamel.

How is it diagnosed?

To find out if someone has a diagnosis of Trisomy 18 syndrome, it is important to have a consultation and evaluation with a clinical genetic specialist.  Specialists may also suggest specific genetic testing or other types of tests to help reach a diagnosis.  FDNA’s AI technology can help speed up the diagnostic process by analyzing facial features and other health information.

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