Rare diseases · Sign or symptom
Trigonocephaly
Triangular skull shape
HP:0000243
What it means
Wedge-shaped, or triangular head, with the apex of the triangle at the midline of the forehead and the base of the triangle at the occiput.
This shape should be assessed from above, with the examiner looking down on the head of the patient. Trigonocephaly can be caused by premature fusion of the metopic suture.
Rare diseases that can present with this32
Very common80–99%
10- C syndrome
- Distal deletion 9p syndrome
- Dysmorphism-cleft palate-loose skin syndrome
- Mandibulofacial dysostosis-microcephaly syndrome
- Monosomy 9p syndrome
- Monosomy 9q22.3 syndrome
- Non-distal duplication 13q syndrome
- Non-syndromic metopic craniosynostosis
- Short stature-craniofacial anomalies-genital hypoplasia syndrome
- Trigonocephaly-short stature-developmental delay syndrome
Common30–79%
6Sometimes5–29%
14- 20q11.2microduplication syndrome
- 2q31.1microdeletion syndrome
- 49,XYYYY syndrome
- Congenital muscular dystrophy with intellectual disability and severe epilepsy
- Congenital progressive bone marrow failure-B-cell immunodeficiency-skeletal dysplasia syndrome
- DPM1-CDG
- Familial scaphocephaly syndrome, McGillivray type
- Helsmoortel-Van der Aa syndrome
and 6 more in this range
The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.
Part of the broader category
Also called: Triangular cranium shape · Triangular head shape · Wedge shaped cranium · Wedge shaped head · Wedge shaped skull
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Start free with EleplanThis page uses the Human Phenotype Ontology (2026-06-23) — Human Phenotype Ontology Consortium, hpo.jax.org. Disease associations from Orphanet (INSERM), CC BY 4.0. Content is educational and is not medical advice.