Rare diseases · Sign or symptom
Open mouth
Gaped jawed appearance
HP:0000194
What it means
A facial appearance characterized by a permanently or nearly permanently opened mouth.
Rare diseases that can present with this54
Very common80–99%
10Common30–79%
23- 16p11.2p12.2microdeletion syndrome
- 2q23.1microdeletion syndrome
- Birk-Barel syndrome
- Christianson syndrome
- Developmental delay-facial dysmorphism syndrome due to MED13L deficiency
- DOORS syndrome
- Down syndrome
- FOXP1 Syndrome
- Houge-Janssens syndrome type 2
- Macrocephaly-intellectual disability-left ventricular non compaction syndrome
- Marshall-Smith syndrome
- Megalocornea-intellectual disability syndrome
- Monosomy 22 syndrome
- Mowat-Wilson syndrome
- Mowat-Wilson syndrome due to a ZEB2 point mutation
- Mowat-Wilson syndrome due to monosomy 2q22
- Neurodevelopmental disorder-craniofacial dysmorphism-cardiac defect-skeletal anomalies syndrome
- Neurodevelopmental disorder-craniofacial dysmorphism-cardiac defect-skeletal anomalies syndrome due to 9q21.3 microdeletion
- Neurodevelopmental disorder-craniofacial dysmorphism-cardiac defect-skeletal anomalies syndrome due to a point mutation
- Non-syndromic bilambdoid and sagittal craniosynostosis
- Primary dystonia, DYT4 type
- Smith-Magenis syndrome
- X-linked creatine transporter deficiency
Sometimes5–29%
21- 5q14.3microdeletion syndrome
- Bainbridge-Ropers syndrome
- Combined oxidative phosphorylation defect type 39
- Dihydropyrimidine dehydrogenase deficiency
- FG syndrome type 1
- Kagami-Ogata syndrome due to maternal 14q32.2 microdeletion
- Laminin subunit alpha 2-related congenital muscular dystrophy
- Macrocephaly-intellectual disability-neurodevelopmental disorder-small thorax syndrome
and 13 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: Gaped mouthed appearance · Open mouth appearance · Slack jawed appearance
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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.