Caring for someone with this diagnosis? Eleplan keeps diagnoses, medications, documents and every specialist in one plan.
Start free with EleplanTrisomy 18 syndrome
ORPHA:3380Malformation syndrome
Also called Chromosome 18 duplication · Edwards syndrome
What it is
A rare chromosomal abnormality characterized by the presence of an extra chromosome 18 material and manifesting with severe intellectual disability growth delay, and extremely variable multiple congenital anomalies, including minor malformations (cranio-facial dysmorphia, short sternum, overlapping fingers) and major malformations, especially cardiac and cerebral. Neurological involvement may lead to seizures and hypotonia.
Key facts
- Prevalence
- 1-9 / 1 000 000 (Europe)
- Age of onset
- Antenatal, Neonatal
- Inheritance
- Not applicable, Unknown
- Classified as
- Malformation syndrome
Prevalence figures describe populations, not individuals, and are often estimates from a single study. Where the figure is an incidence or a birth prevalence, it says so.
Signs and symptoms
Very common80–99%
25- Abnormal cardiovascular system morphology
- Atrial septal defect
- Cachexia
- Camptodactyly of finger
- Cognitive impairment
- Cryptorchidism
- Deviation of finger
- Dolichocephaly
- Global developmental delay
- Growth delay
- Hypertelorism
- Hypertonia
- Hypotonia
- Intellectual disability, severe
- Intrauterine growth retardation
- Microretrognathia
- Narrow palate
- Narrow pelvis bone
- Omphalocele
- Pointed helix
- Posteriorly rotated ears
- Prominent occiput
- Short stature
- Triangular face
- Ventricular septal defect
Common30–79%
31- Abnormality of the fontanelles or cranial sutures
- Abnormality of the hip bone
- Abnormality of the upper urinary tract
- Abnormal morphology of female internal genitalia
- Anal atresia
- Bilateral single transverse palmar creases
- Blepharophimosis
- Brachycephaly
- Central apnea
- Choanal atresia
- Choroid plexus cyst
- Cleft palate
- Congenital diaphragmatic hernia
- Delayed skeletal maturation
- Epicanthus
- Esophageal atresia
- Feeding difficulties in infancy
- Gastroesophageal reflux
- Hernia
- Horseshoe kidney
- Hydronephrosis
- Hypoplasia of the nasal bone
- Increased nuchal translucency
- Microcephaly
- Non-midline cleft of the upper lip
- Overlapping fingers
- Polyhydramnios
- Seizure
- Single umbilical artery
- Small nail
- Talipes equinovarus
These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.
ICD-10 codes
Cross-references
Orphadata Science: Free access data from Orphanet. © INSERM 1999. Data version 2026-06-23. Available under CC BY 4.0. This is a reference, not medical advice.
Powered by Eleplan
A rare diagnosis is just the start. Eleplan keeps the whole care plan in one place.
Diagnoses, medications, documents, appointments, and the whole care team — organized and always in sync, so you are not retelling the same story to every new specialist. With Ellie, your AI care assistant, on top of it. Free to start.