Caring for someone with this diagnosis? Eleplan keeps diagnoses, medications, documents and every specialist in one plan.
Start free with EleplanNoonan syndrome
ORPHA:648Malformation syndrome
What it is
A rare, highly variable, multisystemic disorder mainly characterized by short stature, distinctive facial features, congenital heart defects, cardiomyopathy and an increased risk to develop tumors in childhood.
Key facts
- Prevalence
- 1-5 / 10 000
- Age of onset
- Antenatal, Childhood, Infancy, Neonatal
- Inheritance
- Autosomal dominant, Autosomal recessive
- 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%
29- Abnormal cardiovascular system morphology
- Abnormal EKG
- Abnormality of speech or vocalization
- Aplasia/Hypoplasia of the abdominal wall musculature
- Cystic hygroma
- Downslanted palpebral fissures
- Dysarthria
- Enlarged thorax
- High forehead
- High palate
- Hypertelorism
- Hypogonadotropic hypogonadism
- Joint hypermobility
- Micrognathia
- Midface retrusion
- Muscle weakness
- Pectus carinatum
- Pectus excavatum
- Posteriorly rotated ears
- Proptosis
- Ptosis
- Pulmonary artery stenosis
- Short stature
- Thickened helices
- Thickened nuchal skin fold
- Thick lower lip vermilion
- Triangular face
- Webbed neck
- Wide intermamillary distance
Common30–79%
21- Abnormal bleeding
- Abnormal dermatoglyphics
- Abnormal hair quantity
- Abnormality of coagulation
- Abnormality of the genital system
- Abnormality of the lymphatic system
- Abnormality of the spleen
- Abnormal platelet function
- Abnormal pulmonary valve morphology
- Arrhythmia
- Blue irides
- Coarse hair
- Cryptorchidism
- Delayed skeletal maturation
- Feeding difficulties in infancy
- Hepatomegaly
- Hypotonia
- Low posterior hairline
- Neurodevelopmental delay
- Scoliosis
- Strabismus
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.
Genes
ICD-10 codes
ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.
Related health topics
Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.
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.