Trisomy 18

Genetic MONDO:0018071 Pathograph 6 Show in embeddings browser hereditary disease chromosomal disorder

Trisomy 18 (Edwards syndrome) is a common autosomal trisomy caused by the presence of an extra chromosome 18 — full trisomy in most cases, or mosaic or partial trisomy 18q. It is the second most common autosomal trisomy syndrome after trisomy 21. Whole-chromosome gene-dosage imbalance disrupts development across multiple organ systems, producing prenatal and postnatal growth deficiency, characteristic craniofacial features, a clenched hand with overriding fingers, major malformations (most often cardiac and renal), consistent feeding problems, and marked psychomotor and cognitive disability. Neonatal and infant mortality is high, though a minority of children survive beyond the first year.

Ask OpenScientist

Ask a research question about Trisomy 18. OpenScientist will conduct autonomous deep research using the Disorder Mechanisms Knowledge Base and PubMed literature (typically 10-30 minutes).

Submitting...

Do not include personal health information in your question. Questions and results are cached in your browser's local storage.

5
Pathophys.
8
Phenotypes
6
Pathograph
1
Genes
1
Medical Actions
2
Subtypes
2
References
◆

Subtypes

2
Full (complete) trisomy 18
The most common form — three complete copies of chromosome 18 in all cells, usually arising from meiotic nondisjunction; associated with the full, severe phenotype and high mortality.
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"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."
Distinguishes full trisomy from mosaic and partial 18q forms.
Mosaic trisomy 18 or partial trisomy 18q
Mosaic trisomy (two cell lines) or partial trisomy of 18q. These forms are generally associated with a milder and more variable phenotype and longer survival than full trisomy 18.
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"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."
Establishes mosaic and partial 18q as recognized cytogenetic forms.
⚙

Pathophysiology

5
Trisomy 18 (Extra Chromosome 18)
Presence of a third copy of chromosome 18 (full, mosaic, or partial 18q), most often from meiotic nondisjunction. It is the second most common autosomal trisomy syndrome.
Downstream
Chromosome 18 Gene Dosage Imbalance The extra chromosome raises the dosage of all chromosome 18 genes.
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"The condition is the second most common autosomal trisomy syndrome after trisomy 21."
Establishes trisomy 18 as the second most common autosomal trisomy.
Chromosome 18 Gene Dosage Imbalance
Increased dosage across the genes of chromosome 18 produces a genome-wide developmental disturbance affecting multiple organ systems (cardiac, renal, craniofacial, skeletal, and central nervous system), rather than acting through a single critical gene.
Downstream
Impaired Organogenesis Dosage imbalance disrupts development of the heart and kidneys in particular.
Growth Deficiency
Severe Neurodevelopmental Impairment
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"The recognizable syndrome pattern consists of major and minor anomalies, prenatal and postnatal growth deficiency, an increased risk of neonatal and infant mortality, and marked psychomotor and cognitive disability."
Describes the multisystem developmental pattern resulting from the trisomy.
Impaired Organogenesis
Disrupted organ development, with cardiac and renal malformations the most frequent major anomalies.
heart UBERON:0000948 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in heart (UBERON:0000948). UBERON:0000948 is an anatomical location from the Uberon multi-species anatomy ontology. kidney UBERON:0002113 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in kidney (UBERON:0002113). UBERON:0002113 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Congenital Heart Defects
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"The presence of major malformations is common, and the most frequent are heart and kidney anomalies."
Identifies cardiac and renal malformations as the most frequent major anomalies.
Growth Deficiency
Prenatal and postnatal growth deficiency, compounded by consistent feeding problems.
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"prenatal and postnatal growth deficiency, an increased risk of neonatal and infant mortality, and marked psychomotor and cognitive disability"
Documents prenatal and postnatal growth deficiency as part of the syndrome.
Severe Neurodevelopmental Impairment
Marked psychomotor and cognitive disability in survivors.
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"prenatal and postnatal growth deficiency, an increased risk of neonatal and infant mortality, and marked psychomotor and cognitive disability"
Documents marked psychomotor and cognitive disability.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Trisomy 18 Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

8
Cardiovascular 1
Congenital Heart Defects VERY_FREQUENT Abnormal heart morphology HP:0001627 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Congenital heart defect, annotated with Abnormal heart morphology (HP:0001627). HP:0001627 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"The presence of major malformations is common, and the most frequent are heart and kidney anomalies."
Identifies cardiac anomalies as one of the most frequent major malformations.
Digestive 1
Feeding Difficulties VERY_FREQUENT HP:0011968 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Feeding difficulties (HP:0011968). HP:0011968 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"Feeding problems occur consistently and may require enteral nutrition."
States that feeding problems occur consistently and may require enteral nutrition.
Genitourinary 1
Renal Anomalies FREQUENT Abnormality of the kidney HP:0000077 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Kidney anomaly, annotated with Abnormality of the kidney (HP:0000077). HP:0000077 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"The presence of major malformations is common, and the most frequent are heart and kidney anomalies."
Identifies renal anomalies as one of the most frequent major malformations.
Head and Neck 1
Micrognathia FREQUENT HP:0000347 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Micrognathia (HP:0000347). HP:0000347 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:32522368 SUPPORT Human Clinical
"anatomical features included micrognathia/mandibular hypoplasia, small mouth/small airway, midface hypoplasia, abnormal/difficult airway, glossoptosis, hypotonia, and GERD"
Lists micrognathia/mandibular hypoplasia among the anatomical features in trisomy 18/13.
Nervous System 2
Severe Intellectual Disability VERY_FREQUENT HP:0010864 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Marked psychomotor and cognitive disability, annotated with Severe intellectual disability (HP:0010864). HP:0010864 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"prenatal and postnatal growth deficiency, an increased risk of neonatal and infant mortality, and marked psychomotor and cognitive disability"
Documents marked psychomotor and cognitive disability in survivors.
Obstructive Sleep Apnea OCCASIONAL HP:0002870 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Obstructive sleep apnea (HP:0002870). HP:0002870 is a phenotype from the Human Phenotype Ontology.
Related to micrognathia, midface hypoplasia, glossoptosis, and airway anomalies; upper-airway obstruction may be underrecognized.
Show evidence (1 reference)
PMID:32522368 SUPPORT Human Clinical
"The results of our study suggest that T13 and T18 patients are at increased risk for OSA due to common features found in this population."
Reports increased risk of obstructive sleep apnea from the anatomical features common in trisomy 18/13.
Growth 1
Growth Deficiency VERY_FREQUENT Growth delay HP:0001510 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Prenatal and postnatal growth deficiency, annotated with Growth delay (HP:0001510). HP:0001510 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"prenatal and postnatal growth deficiency, an increased risk of neonatal and infant mortality, and marked psychomotor and cognitive disability"
Lists prenatal and postnatal growth deficiency as a core feature.
Other 1
Clenched Hand with Overlapping Fingers VERY_FREQUENT HP:0010557 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Clenched hand with overriding fingers, annotated with Overlapping fingers (HP:0010557). HP:0010557 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"Typical minor anomalies include characteristic craniofacial features, clenched fist with overriding fingers, small fingernails, underdeveloped thumbs, and short sternum."
Lists the clenched fist with overriding fingers, a hallmark sign of trisomy 18.
🧬

Genetic Associations

1
Trisomy 18 (extra chromosome 18) (Causal)
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"The recurrence risk for a family with a child with full trisomy 18 is about 1%."
Provides the recurrence risk for full trisomy 18.
💊

Medical Actions

1
Supportive and Palliative Care
Action: supportive careNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is supportive care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. Ontology label: Supportive Care NCIT:C15747
No curative therapy exists. Management is supportive and individualized — feeding/nutritional support (often enteral), respiratory and airway care, and diligent health supervision, especially in the first year of life. Decisions about the intensity of care are made with the family.
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"Health supervision should be diligent, especially in the first 12 months of life, and can require multiple pediatric and specialist evaluations."
Supports diligent multidisciplinary health supervision as the management approach.
🔬

Diagnosis

1
Karyotype Analysis (47,XX,+18 or 47,XY,+18)
Most cases are now diagnosed prenatally (maternal-age/serum screening, sonographic markers) and confirmed by karyotype.
Show evidence (1 reference)
PMID:23088440 SUPPORT Human Clinical
"Currently most cases of trisomy 18 are prenatally diagnosed, based on screening by maternal age, maternal serum marker screening, or detection of sonographic abnormalities"
Establishes prenatal screening and diagnosis as the usual ascertainment route.
📊

Prevalence

1
Live births
Birth Prevalence 14.0 per 100,000 (12.5–16.7) 1–9 per 10,000
Live-born prevalence ~1 in 6,000 to 1 in 8,000 (12.5-16.7 per 100,000). Overall prevalence is higher (~1 in 2,500-2,600) because of frequent fetal loss and pregnancy termination after prenatal diagnosis. Risk rises with maternal age.
Show evidence (2 references)
PMID:23088440 SUPPORT Human Clinical
"The live born prevalence is estimated as 1/6,000-1/8,000"
Provides the live-born prevalence estimate.
PMID:23088440 SUPPORT Human Clinical
"The prevalence of trisomy 18 rises with the increasing maternal age."
Documents the maternal-age effect on prevalence.
{ }

Source YAML

click to show 
name: Trisomy 18
creation_date: "2026-08-22T00:00:00Z"
description: >-
  Trisomy 18 (Edwards syndrome) is a common autosomal trisomy caused by the
  presence of an extra chromosome 18 — full trisomy in most cases, or mosaic or
  partial trisomy 18q. It is the second most common autosomal trisomy syndrome
  after trisomy 21. Whole-chromosome gene-dosage imbalance disrupts development
  across multiple organ systems, producing prenatal and postnatal growth
  deficiency, characteristic craniofacial features, a clenched hand with overriding
  fingers, major malformations (most often cardiac and renal), consistent feeding
  problems, and marked psychomotor and cognitive disability. Neonatal and infant
  mortality is high, though a minority of children survive beyond the first year.
category: Genetic
synonyms:
- Edwards syndrome
- trisomy 18 syndrome
- complete trisomy 18
parents:
- hereditary disease
- chromosomal disorder
disease_term:
  preferred_term: trisomy 18
  term:
    id: MONDO:0018071
    label: trisomy 18
has_subtypes:
- name: Full trisomy 18
  display_name: Full (complete) trisomy 18
  description: >-
    The most common form — three complete copies of chromosome 18 in all cells,
    usually arising from meiotic nondisjunction; associated with the full,
    severe phenotype and high mortality.
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "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."
    explanation: Distinguishes full trisomy from mosaic and partial 18q forms.
- name: Mosaic or partial trisomy 18
  display_name: Mosaic trisomy 18 or partial trisomy 18q
  description: >-
    Mosaic trisomy (two cell lines) or partial trisomy of 18q. These forms are
    generally associated with a milder and more variable phenotype and longer
    survival than full trisomy 18.
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "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."
    explanation: Establishes mosaic and partial 18q as recognized cytogenetic forms.
prevalence:
- population: Live births
  measure_type: BIRTH_PREVALENCE
  prevalence_class: BAND_1_5_PER_10000
  rate_per_100000: 14.0
  rate_low: 12.5
  rate_high: 16.7
  notes: >-
    Live-born prevalence ~1 in 6,000 to 1 in 8,000 (12.5-16.7 per 100,000). Overall
    prevalence is higher (~1 in 2,500-2,600) because of frequent fetal loss and
    pregnancy termination after prenatal diagnosis. Risk rises with maternal age.
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The live born prevalence is estimated as 1/6,000-1/8,000"
    explanation: Provides the live-born prevalence estimate.
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The prevalence of trisomy 18 rises with the increasing maternal age."
    explanation: Documents the maternal-age effect on prevalence.
pathophysiology:
- name: Trisomy 18 (Extra Chromosome 18)
  biological_scale: MOLECULAR
  description: >-
    Presence of a third copy of chromosome 18 (full, mosaic, or partial 18q),
    most often from meiotic nondisjunction. It is the second most common
    autosomal trisomy syndrome.
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The condition is the second most common autosomal trisomy syndrome after trisomy 21."
    explanation: Establishes trisomy 18 as the second most common autosomal trisomy.
  downstream:
  - target: Chromosome 18 Gene Dosage Imbalance
    causal_link_type: DIRECT
    description: The extra chromosome raises the dosage of all chromosome 18 genes.
- name: Chromosome 18 Gene Dosage Imbalance
  biological_scale: MOLECULAR
  description: >-
    Increased dosage across the genes of chromosome 18 produces a genome-wide
    developmental disturbance affecting multiple organ systems (cardiac, renal,
    craniofacial, skeletal, and central nervous system), rather than acting
    through a single critical gene.
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The recognizable syndrome pattern consists of major and minor anomalies, prenatal and postnatal growth deficiency, an increased risk of neonatal and infant mortality, and marked psychomotor and cognitive disability."
    explanation: Describes the multisystem developmental pattern resulting from the trisomy.
  downstream:
  - target: Impaired Organogenesis
    causal_link_type: DIRECT
    description: Dosage imbalance disrupts development of the heart and kidneys in particular.
  - target: Growth Deficiency
    causal_link_type: DIRECT
  - target: Severe Neurodevelopmental Impairment
    causal_link_type: DIRECT
- name: Impaired Organogenesis
  biological_scale: TISSUE
  description: >-
    Disrupted organ development, with cardiac and renal malformations the most
    frequent major anomalies.
  locations:
  - preferred_term: heart
    term:
      id: UBERON:0000948
      label: heart
  - preferred_term: kidney
    term:
      id: UBERON:0002113
      label: kidney
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The presence of major malformations is common, and the most frequent are heart and kidney anomalies."
    explanation: Identifies cardiac and renal malformations as the most frequent major anomalies.
  downstream:
  - target: Congenital Heart Defects
    causal_link_type: DIRECT
- name: Growth Deficiency
  biological_scale: ORGANISM
  description: Prenatal and postnatal growth deficiency, compounded by consistent feeding problems.
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "prenatal and postnatal growth deficiency, an increased risk of neonatal and infant mortality, and marked psychomotor and cognitive disability"
    explanation: Documents prenatal and postnatal growth deficiency as part of the syndrome.
- name: Severe Neurodevelopmental Impairment
  biological_scale: ORGANISM
  description: Marked psychomotor and cognitive disability in survivors.
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "prenatal and postnatal growth deficiency, an increased risk of neonatal and infant mortality, and marked psychomotor and cognitive disability"
    explanation: Documents marked psychomotor and cognitive disability.
phenotypes:
- category: Growth
  name: Growth Deficiency
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Prenatal and postnatal growth deficiency
    term:
      id: HP:0001510
      label: Growth delay
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "prenatal and postnatal growth deficiency, an increased risk of neonatal and infant mortality, and marked psychomotor and cognitive disability"
    explanation: Lists prenatal and postnatal growth deficiency as a core feature.
- category: Neurologic
  name: Severe Intellectual Disability
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Marked psychomotor and cognitive disability
    term:
      id: HP:0010864
      label: Severe intellectual disability
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "prenatal and postnatal growth deficiency, an increased risk of neonatal and infant mortality, and marked psychomotor and cognitive disability"
    explanation: Documents marked psychomotor and cognitive disability in survivors.
- category: Musculoskeletal
  name: Clenched Hand with Overlapping Fingers
  frequency: VERY_FREQUENT
  diagnostic: true
  phenotype_term:
    preferred_term: Clenched hand with overriding fingers
    term:
      id: HP:0010557
      label: Overlapping fingers
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Typical minor anomalies include characteristic craniofacial features, clenched fist with overriding fingers, small fingernails, underdeveloped thumbs, and short sternum."
    explanation: Lists the clenched fist with overriding fingers, a hallmark sign of trisomy 18.
- category: Cardiac
  name: Congenital Heart Defects
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Congenital heart defect
    term:
      id: HP:0001627
      label: Abnormal heart morphology
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The presence of major malformations is common, and the most frequent are heart and kidney anomalies."
    explanation: Identifies cardiac anomalies as one of the most frequent major malformations.
- category: Renal
  name: Renal Anomalies
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Kidney anomaly
    term:
      id: HP:0000077
      label: Abnormality of the kidney
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The presence of major malformations is common, and the most frequent are heart and kidney anomalies."
    explanation: Identifies renal anomalies as one of the most frequent major malformations.
- category: Gastrointestinal
  name: Feeding Difficulties
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Feeding problems occur consistently and may require enteral nutrition."
    explanation: States that feeding problems occur consistently and may require enteral nutrition.
- category: Craniofacial
  name: Micrognathia
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Micrognathia
    term:
      id: HP:0000347
      label: Micrognathia
  evidence:
  - reference: PMID:32522368
    reference_title: "Sleep disordered breathing in children with trisomy 13 and trisomy 18."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "anatomical features included micrognathia/mandibular hypoplasia, small mouth/small airway, midface hypoplasia, abnormal/difficult airway, glossoptosis, hypotonia, and GERD"
    explanation: Lists micrognathia/mandibular hypoplasia among the anatomical features in trisomy 18/13.
- category: Respiratory
  name: Obstructive Sleep Apnea
  frequency: OCCASIONAL
  notes: Related to micrognathia, midface hypoplasia, glossoptosis, and airway anomalies; upper-airway obstruction may be underrecognized.
  phenotype_term:
    preferred_term: Obstructive sleep apnea
    term:
      id: HP:0002870
      label: Obstructive sleep apnea
  evidence:
  - reference: PMID:32522368
    reference_title: "Sleep disordered breathing in children with trisomy 13 and trisomy 18."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The results of our study suggest that T13 and T18 patients are at increased risk for OSA due to common features found in this population."
    explanation: Reports increased risk of obstructive sleep apnea from the anatomical features common in trisomy 18/13.
genetic:
- name: Trisomy 18 (extra chromosome 18)
  association: Causal
  notes: >-
    Presence of an extra copy of chromosome 18 — full trisomy (most cases,
    typically from meiotic nondisjunction), mosaic trisomy, or partial trisomy
    18q (copy-number gain). The recurrence risk after a child with full trisomy 18
    is about 1%; prevalence rises with maternal age. No coordinate slot exists in
    the schema; the whole-chromosome gain is recorded here in prose.
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The recurrence risk for a family with a child with full trisomy 18 is about 1%."
    explanation: Provides the recurrence risk for full trisomy 18.
diagnosis:
- name: Karyotype Analysis
  presence: 47,XX,+18 or 47,XY,+18
  notes: Most cases are now diagnosed prenatally (maternal-age/serum screening, sonographic markers) and confirmed by karyotype.
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Currently most cases of trisomy 18 are prenatally diagnosed, based on screening by maternal age, maternal serum marker screening, or detection of sonographic abnormalities"
    explanation: Establishes prenatal screening and diagnosis as the usual ascertainment route.
treatments:
- name: Supportive and Palliative Care
  description: >-
    No curative therapy exists. Management is supportive and individualized —
    feeding/nutritional support (often enteral), respiratory and airway care, and
    diligent health supervision, especially in the first year of life. Decisions
    about the intensity of care are made with the family.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:23088440
    reference_title: "The trisomy 18 syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Health supervision should be diligent, especially in the first 12 months of life, and can require multiple pediatric and specialist evaluations."
    explanation: Supports diligent multidisciplinary health supervision as the management approach.
references:
- reference: PMID:23088440
  title: "The trisomy 18 syndrome."
- reference: PMID:32522368
  title: "Sleep disordered breathing in children with trisomy 13 and trisomy 18."
📚

References & Deep Research

References

2
PMID:23088440
The trisomy 18 syndrome.
No top-level findings curated for this source.
PMID:32522368
Sleep disordered breathing in children with trisomy 13 and trisomy 18.
No top-level findings curated for this source.