Difference Between Trisomy 13 and 18

Key Difference – Trisomy 13 vs 18
 

Genetic abnormalities in infants are perhaps the most unfortunate group of diseases. The physical and psychological impact they have on the parents and baby is immense. Trisomy 13 and trisomy 18, which are also known as Patau syndrome and Edward syndrome respectively, are two of the most complicated genetic defects seen in a fair number of pregnancies throughout the world. The key difference between trisomy 13 and 18 is that in trisomy 13, there is an extra copy in chromosome 13 whereas, in trisomy 18, it is chromosome 18 that has an extra copy.

CONTENTS

1. Overview and Key Difference
2. What is Trisomy 13 (Patau Syndrome)
3. What is Trisomy 18 (Edward Syndrome)
4. Similarities Between Trisomy 13 and 18
5. Side by Side Comparison – Trisomy 13 vs 18 in Tabular Form
6. Summary

What is Trisomy 13?

Trisomy 13, also known as the Patau Syndrome, is a genetic abnormality characterized by the presence of an extra copy in the chromosome 13. 1in every 5000 people are affected by this condition.

Clinical Features

• Low set ears
• Cleft lip and palate
• Polydactyly
• Microophthalmia
• Learning difficulties
• Patients rarely survive for more than few weeks

Definitive diagnosis of Patau syndrome in the prenatal period is through the genetic analysis of the samples obtained from amniocentesis and chorionic villus sampling. CT and MRI can be used for the identification of abnormalities in the heart, brain, and other organs.

Management

Most infants with Patau syndrome do not make it to the first year of life. They die because of life-threatening neurological complications and cardiac problems. Surgical correction of deformities such as cleft palate may be necessary.

What is Trisomy 18?

Trisomy 18, also known as Edward Syndrome, is another autosomal genetic disorder that is caused by the presence of an extra copy of chromosome 18. Edward syndrome has a correlation with the maternal age.

Although trisomy 18 shares several common clinical features with trisomy 21, these clinical features are much more severe; therefore, the patient does not survive beyond the first year of life. Most of the affected infants succumb within the first few weeks.

Clinical Features

• Prominent occiput
• Mental retardation
• Overlapping fingers
• Rocker bottom feet
• Congenital heart defects
• Micrognathia
• Low set ears
• Short neck
• Renal malformations
• Limited hip abduction

Management

There is no cure for the trisomy 18. The occurrence of infections should be prevented, and complications should be minimized. Whenever a patient gets an infection, it should be treated promptly and vigorously. Special care has to be given for the management of heart defects and renal abnormalities.

What are the Similarities Between Trisomy 13 and 18?

• Both diseases are genetic conditions that are due to the presence of extra genetic materials
• Diagnosis of both diseases is through the samples obtained from amniocentesis and chorionic villus sampling.

What is the Difference Between Trisomy 13 and 18?

Summary – Trisomy 13 vs 18

Trisomy 13 and trisomy 18 are two genetic disorders which are also known as Patau syndrome and Edward syndrome respectively. The main difference between the trisomy 13 and 18 is that, in trisomy 13 or Patau syndrome, the defect is in chromosome 13, but in trisomy 18 or Edward syndrome, the defect is in chromosome 18.

Reference:

1.Kumar, Parveen J., and Michael L. Clark. Kumar & Clark clinical medicine. Edinburgh: W.B. Saunders, 2009.

Image Courtesy:

1. “Full Trisomy 13 phenotype” By TRIsoMY Favorite Things Inspired By Natalia’s Trisomy 13 LIFE – Facebook (CC BY 4.0) via Commons Wikimedia
2. “Chromosome 18” By Mysid – Made by Mysid, based on http://ghr.nlm.nih.gov/chromosome=18 (National Library of Medicine) (Public Domain) via Commons Wikimedia