Rare diseases · Sign or symptom
Smooth philtrum
HP:0000319
What it means
Flat skin surface, with no ridge formation in the central region of the upper lip between the nasal base and upper vermilion border.
There is a spectrum of this finding from total absence of the philtral ridges to a some prominence of the ridges. The central groove varies from absent to shallow. Normal values for the frequency of smooth philtrum are available. Grading of the smoothness of the philtrum, used in the assessment of Fetal Alcohol Syndrome, has been developed. This finding is greatly influenced by the facial expression, and care should be taken to evaluate the philtrum when the face is in a neutral position. A smooth philtrum can be associated with a Long philtrum. However, the two findings should be coded separately.
Rare diseases that can present with this76
Very common80–99%
19- 2p15p16.1microdeletion syndrome
- Acrofacial dysostosis, Catania type
- Adenylosuccinate lyase deficiency
- AREDYLD syndrome
- Autosomal recessive cutis laxa type 2, classic type
- Craniolenticulosutural dysplasia
- C syndrome
- Distal 22q11.2 microdeletion syndrome
- Distal deletion 1q syndrome
- Facial dysmorphism-shawl scrotum-joint laxity syndrome
- Faciocardiorenal syndrome
- Microtriplication 11q24.1 syndrome
- Müllerian derivatives-lymphangiectasia-polydactyly syndrome
- Nicolaides-Baraitser syndrome
- Perlman syndrome
- Proximal 16p11.2 microduplication syndrome
- Sialuria
- Trisomy 4p syndrome
- Wrinkly skin syndrome
Common30–79%
23- 15q24microdeletion syndrome
- 16q24.3microdeletion syndrome
- 1q44microdeletion syndrome
- 20p13microdeletion syndrome
- 8q24.3microdeletion syndrome
- Cleft palate-congenital heart defect-intellectual disability syndrome due to 15q14 microdeletion
- COG1-CDG
- Distal deletion 6p syndrome
- Fetal alcohol syndrome
- FOXG1 syndrome due to 14q12 microdeletion
- Growth delay due to insulin-like growth factor I resistance
- Hypotonia-speech impairment-severe cognitive delay syndrome
- Jacobsen syndrome
- Lateral meningocele syndrome
- Maternal uniparental disomy of chromosome 1 syndrome
- MOMO syndrome
- Multiple sulfatase deficiency
- Oculocerebrofacial syndrome, Kaufman type
- Pierpont syndrome
- PLAA-associated neurodevelopmental disorder
- SATB2-associated syndrome due to a pathogenic variant
- THOC6-related developmental delay-microcephaly-facial dysmorphism syndrome
- Toluene embryopathy
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: Decreased depth of philtrum · Flat philtrum · Indistinct philtrum · Philtrum, smooth · Shallow philtrum · Simple philtrum
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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.