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ORPHA:818Malformation syndrome
Also called 7-dehydrocholesterol reductase deficiency · RSH syndrome · SLOS
What it is
A rare genetic developmental disorder characterized by multiple congenital anomalies (pre- and postnatal growth retardation, microcephaly, male genital anomalies), intellectual disability, and behavioral problems.
Key facts
- Prevalence
- 1-9 / 100 000 (at birth, Europe)
- Age of onset
- Antenatal, Infancy, 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%
16- 2-3 toe syndactyly
- Abnormal dental morphology
- Abnormal dermatoglyphics
- Anteverted nares
- Elevated 7-dehydrocholesterol
- Feeding difficulties in infancy
- Gastroesophageal reflux
- Global developmental delay
- Growth delay
- Hypotonia
- Increased nuchal translucency
- Intellectual disability
- Microcephaly
- Micrognathia
- Short stature
- Wide nasal bridge
Common30–79%
40- Abnormal cardiovascular system morphology
- Abnormality of the larynx
- Abnormal lung lobation
- Abnormal metacarpal morphology
- Ambiguous genitalia
- Aplasia/Hypoplasia of the cerebellum
- Atrial septal defect
- Atrioventricular canal defect
- Attention deficit hyperactivity disorder
- Autism
- Biparietal narrowing
- Cleft palate
- Clitoral hypertrophy
- Cryptorchidism
- Cutaneous photosensitivity
- Cutis marmorata
- Excessive daytime somnolence
- Facial capillary hemangioma
- Gingival overgrowth
- Hip dislocation
- Hypoplasia of penis
- Hypospadias
- Intrauterine growth retardation
- Long philtrum
- Polyhydramnios
- Postaxial foot polydactyly
- Postaxial hand polydactyly
- Posteriorly rotated ears
- Proximal placement of thumb
- Ptosis
- Pulmonary hypoplasia
- Recurrent infections
- Self-injurious behavior
- Short neck
- Sleep abnormality
- Tracheal stenosis
- Ventricular septal defect
- Ventriculomegaly
- Wide intermamillary distance
- Wide mouth
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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