Trisomy 18: Difference between revisions

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(Edwards Syndrome, 18T) An aneuploidy, first recognized as a specific clinical entity by the discovery of an extra chromosome 18 in babies with a particular pattern of malformation by independent groups.<ref><pubmed>13819419</pubmed></ref> <ref><pubmed>14430807</pubmed></ref> <ref><pubmed>13831938</pubmed></ref>
(Edwards Syndrome, 18T) An aneuploidy, first recognized as a specific clinical entity by the discovery of an extra chromosome 18 in babies with a particular pattern of malformation by independent groups.<ref><pubmed>13819419</pubmed></ref> <ref><pubmed>14430807</pubmed></ref> <ref><pubmed>13831938</pubmed></ref>


In many cases associated abnormalities include: fetal growth restriction, polyhydramnios and congenital heart defects.


Both trisomy 13 and trisomy 18 are generally considered fatal anomalies, with a majority of infants dying in the first year after birth.<ref><pubmed>22492767</pubmed></ref>
Both trisomy 13 and trisomy 18 are generally considered fatal anomalies, with a majority of infants dying in the first year after birth<ref><pubmed>22492767</pubmed></ref>, see also recent [[#Survival Rate|Japanese study]].<ref name=PMID26104883><pubmed>26104883</pubmed></ref>




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Survival Rate from 73 live-born infants<ref name=PMID26104883><pubmed>26104883</pubmed></ref>  
==Survival Rate==
Stillbirths occurs prenatally in 40% cases with fetal demise also before onset and during labor.
 
From a Japanese study of 73 live-born infants<ref name=PMID26104883><pubmed>26104883</pubmed></ref>  
 
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Chromosome- trisomy 18.jpg

Introduction

Karyotype Trisomy 18 male

(Edwards Syndrome, 18T) An aneuploidy, first recognized as a specific clinical entity by the discovery of an extra chromosome 18 in babies with a particular pattern of malformation by independent groups.[1] [2] [3]

In many cases associated abnormalities include: fetal growth restriction, polyhydramnios and congenital heart defects.

Both trisomy 13 and trisomy 18 are generally considered fatal anomalies, with a majority of infants dying in the first year after birth[4], see also recent Japanese study.[5]


International Classification of Diseases: Q91 Edwards' syndrome and Patau's syndrome


Genetic Links: genetic abnormalities | maternal age | Trisomy 21 | Trisomy 18 | Trisomy 13 | Trisomy X | trisomy mosaicism | Monosomy | Fragile X | Williams | Alagille | Philadelphia chromosome | mitochondria | VACTERL | hydatidiform mole | epigenetics | Prenatal Diagnosis | Neonatal Diagnosis | meiosis | mitosis | International Classification of Diseases | genetics

Some Recent Findings

  • Fetal outcome of trisomy 18 diagnosed after 22 weeks of gestation: Experience of 123 cases at a single perinatal center[5] "To investigate the pregnancy outcome of the fetuses with trisomy 18, we studied 123 cases of trisomy 18 who were born at our hospital from 1993 to 2009. Among them, 95.9% were diagnosed with trisomy 18 prenatally. Prenatal ultrasound findings showed fetal growth restriction in 77.2%, polyhydramnios in 63.4% and congenital heart defects in 95.1%. For 18 cases, cesarean section (C-section) was chosen, and for 75 cases, transvaginal delivery was chosen. Premature delivery occurred in 35.5%. Stillbirths occurred in 50 cases (40.7%). Fetal demise before onset of labor occurred in 30 cases and fetal demise during labor occurred in 20 cases which was 26.7% of vaginal deliveries. Among the 73 live-born infants, the survival rate for 24 h, 1 week, 1 month and 1 year were 63%, 43%, 33% and 3%. The median survival time was 3.5 days."
  • Recent Trisomy 18 Review. [6] "The trisomy 18 syndrome, also known as Edwards syndrome, is a common chromosomal disorder due to the presence of an extra chromosome 18, either full, mosaic trisomy, or partial trisomy 18q. The condition is the second most common autosomal trisomy syndrome after trisomy 21. The live born prevalence is estimated as 1/6,000-1/8,000, but the overall prevalence is higher (1/2500-1/2600) due to the high frequency of fetal loss and pregnancy termination after prenatal diagnosis. The prevalence of trisomy 18 rises with the increasing maternal age. The recurrence risk for a family with a child with full trisomy 18 is about 1%. Currently most cases of trisomy 18 are prenatally diagnosed, based on screening by maternal age, maternal serum marker screening, or detection of sonographic abnormalities (e.g., increased nuchal translucency thickness, growth retardation, choroid plexus cyst, overlapping of fingers, and congenital heart defects). "
  • Consensus statement: chromosomal microarray is a first-tier clinical diagnostic test for individuals with developmental disabilities or congenital anomalies[7]
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<pubmed limit=5>Trisomy 18</pubmed>


Survival Rate

Stillbirths occurs prenatally in 40% cases with fetal demise also before onset and during labor.

From a Japanese study of 73 live-born infants[5]

Time Percentage
24 h 63%
1 week 43%
1 month 33%
1 year 3%

Prevalence

Syndrome abnormalities USA 1998-2008 graph.jpg

Abnormalities from USA Nationwide Inpatient Sample database (1998 to 2008)[8]

Features

Frequency Organ/System Prevalent type of malformation
Common (>75%) heart septal defects, patent ductus arteriosus, and polyvalvular disease
Frequent (25-75%) genitourinary horseshoe kidney
Less frequent (5-25%) gastrointestinal

central nervous system

craniofacial

eye

limb

omphalocele, esophageal atresia with tracheo-esophageal fistula, pyloric stenosis, Meckel diverticulum

cerebellar hypoplasia, agenesis of corpus callosum, polymicrogyria, spina bifida

orofacial clefts

microphthalmia, coloboma, cataract, corneal opacities

radial aplasia/hypoplasia

Table modified from[6]

Pedbase Entry

Definition

A chromosomal disorder resulting in a syndrome characterized by specific (small) dysmorphic features and organ malformations.

Epidemiology

incidence: 1/8000 live births most die in embryonic or fetal life 2nd most common autosomal aberration 2nd most common multiple malformation syndrome age of onset: newborn risk factors: advanced maternal age F > M (4:1)

History

1960 first recognized as a specific clinical entity by the discovery of an extra chromosome 18 in babies with a particular pattern of malformation by three independent groups (Edwards et al., Patau et al., Smith et al.)

Pathogenesis - Genetics

Trisomy 18

90% of cases due to meiotic nondisjunction less than 1% recurrence rate

Mosaicism

10% of cases due to postzygotic (postfertilization) mitotic nondisjunction leads to the partial clinical expression of Trisomy 18 with a longer survival

Translocations

very rare give rise to partial trisomy 18 syndromes short arm: causes non-specific clinical features with mild or no mental deficiency long arm: entire: clinically indistinguishable from trisomy 18 distal 1/3 -> : partial clinical picture of trisomy 18 with a longer survival and less profound mental retardation

Clinical Features

Dysmorphic Features

1. Facial

  • microcephaly with prominent occiput
  • narrow bifrontal diameter
  • short palpabral fissures
  • low-set malformed ears
  • cleft lip +/- palate
  • narrow palatal arch
  • micrognathia

2. Skeletal

  • neck - webbed
  • chest - short sternum, widely spaced nipples
  • hips - small pelvis, congenital dislocation of the hips, limited hip abduction
  • extremities - phocomelia, rockerbottom feet or equinovarus, short dorsiflexed big toes, fixed flexion deformity of the fingers (overlapping of the 2nd and 5th fingers over the 3rd and 4th fingers), simple arch pattern of the fingers and toes, hypoplasia of fingernails, single crease of 5th finger or all fingers (absence of interphalangeal flexion creases), simian crease

Organ Malformations

1. Central Nervous System

  • severe mental retardation
  • hypotonia -> hypertonia
  • neural tube defects
  • poor suck and weak cry
  • failure to thrive
  • ocular anomalies

2. Respiratory

  • apnea

3. Cardiovascular( >95%)

  • major: VSD, ASD, PDA
  • minor: transposition, ToF, coarctation, anomalous coronary artery, dextrocardia, aberrant subclavian artery, arteriosclerosis, PS, bicuspid aortic and/or pulmonic valves

4. Gastrointestinal

  • inguinal, umbilical, and/or diaphragmatic hernia
  • congenital defects: diastasis recti, heterotopic pancreas, malrotation, Meckel's, tracheoesophageal fistula

5. Genitourinary

  • cryptorchidism
  • congenital defects: double ureter, ectopic kidney, horseshoe kidney, hydronephrosis, polycystic kidney

Investigations

Imaging Studies

  • to rule out organ malformations:
  • cardiovascular anomalies - Echo
  • gastrointestinal anomalies - Barium Swallow, Endoscope
  • genitourinary anomalies - Ultrasound

Karyotyping

Management

Supportive, very poor prognosis.

  • 30% dying by 1 month of age
  • 50% dying by 2 months of age
  • 90% dying by 12 months of age

Genetic counselling, recurrence rate depends on genotype.

(modified from original 1999 Pedbase entry)

References

  1. <pubmed>13819419</pubmed>
  2. <pubmed>14430807</pubmed>
  3. <pubmed>13831938</pubmed>
  4. <pubmed>22492767</pubmed>
  5. 5.0 5.1 5.2 <pubmed>26104883</pubmed>
  6. 6.0 6.1 <pubmed>23088440</pubmed>| Orphanet J Rare Dis.
  7. <pubmed>20466091</pubmed>
  8. <pubmed>24987252</pubmed>| Ann Pediatr Cardiol.

Reviews

<pubmed></pubmed> <pubmed></pubmed> <pubmed></pubmed> <pubmed>23088440</pubmed>

Articles

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Search Pubmed: trisomy 13 | Edwards Syndrome

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Cite this page: Hill, M.A. (2024, March 29) Embryology Trisomy 18. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Trisomy_18

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