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Start free with EleplanNon-syndromic bilambdoid and sagittal craniosynostosis
ORPHA:1516Malformation syndrome
Also called BLSS · Bilateral lambdoid and sagittal synostosis · Isolated sagittal and bilambdoid craniosynostosis · Non-syndromic sagittal and bilateral lambdoid synostosis
What it is
A rare cranial malformation syndrome characterized by the premature closure of both lambdoid sutures and the posterior sagittal suture, resulting in abnormal skull contour (frontal bossing, anterior turricephaly with mild brachycephaly, biparietal narrowing, occipital concavity) and dysmorphic facial features (low-set ears, midfacial hypoplasia). Short stature, developmental delay, epilepsy, and oculomotor dyspraxia have also been reported. Associated anomalies include enlargement of the cerebral ventricles, agenesis of the corpus callosum, Arnold-Chiari malformation type I, venous anomalies of skull, and hydrocephalus.
Key facts
- Prevalence
- <1 / 1 000 000
- Age of onset
- Neonatal
- Inheritance
- 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%
7Common30–79%
13Sometimes5–29%
9- Abnormal oral cavity morphology
- Epicanthus
- Facial asymmetry
- Hypoplasia of the corpus callosum
- Nevus flammeus
- Nystagmus
- Patent ductus arteriosus
- Sacral dimple
and 1 more in this range
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.
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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