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ORPHA:1308Malformation syndrome
Also called OTCS · Opitz C trigonocephaly · Opitz trigonocephaly C syndrome · Opitz trigonocephaly syndrome · Trigonocephaly C syndrome
What it is
C syndrome is a rare multiple congenital anomaly/intellectual disability syndrome characterized by trigonocephaly and metopic suture synostosis, dysmorphic facial features, short neck, skeletal anomalies, and variable intellectual disability.
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%
20- Anteverted nares
- Biparietal narrowing
- Clinodactyly of the 5th finger
- Cryptorchidism
- Depressed nasal bridge
- Epicanthus
- Female pseudohermaphroditism
- Gingival overgrowth
- High palate
- Hypoplasia of the ear cartilage
- Intellectual disability
- Long philtrum
- Microcephaly
- Micrognathia
- Posteriorly rotated ears
- Short neck
- Short nose
- Smooth philtrum
- Trigonocephaly
- Upslanted palpebral fissure
Common30–79%
20- Abnormal cardiovascular system morphology
- Abnormality of immune system physiology
- Abnormality of the anus
- Accessory oral frenulum
- Bilateral single transverse palmar creases
- Dislocated radial head
- Failure to thrive in infancy
- Hypotonia
- Joint dislocation
- Limitation of joint mobility
- Micromelia
- Midline facial capillary hemangioma
- Pectus excavatum
- Redundant skin
- Sacral dimple
- Seizure
- Short stature
- Strabismus
- Talipes
- Thin vermilion border
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.
Gene
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.
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