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Start free with EleplanSIM1-related Prader-Willi-like syndrome
ORPHA:398079Disease
Also called SIM1-related PWLS
What it is
A rare Prader-Willi-like syndrome characterized by severe obesity due to SIM1 mutation, in addition to some clinical features of Prader-Willi- syndrome including intellectual disability, developmental delay, behaviour problems and facial dysmorphism. Unlike Prader-Willi syndrome, short stature, hypotonia and hypogonadism may not be observed.
Key facts
- Prevalence
- <1 / 1 000 000
- Age of onset
- Antenatal, Infancy, Neonatal
- Inheritance
- Autosomal dominant
- Classified as
- Disease
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%
31- Abdominal obesity
- Abnormal temper tantrums
- Absence of pubertal development
- Atypical behavior
- Autistic behavior
- Brain imaging abnormality
- Clitoral hypoplasia
- Decreased testicular size
- Delayed speech and language development
- External genital hypoplasia
- Failure to thrive
- Hypogonadotropic hypogonadism
- Hypoplastic labia minora
- Hypothalamic luteinizing hormone-releasing hormone deficiency
- Intellectual disability
- Nasogastric tube feeding
- Neonatal hypotonia
- Neurodevelopmental delay
- Polyphagia
- Primary amenorrhea
- Reduced tendon reflexes
- Scoliosis
- Short foot
- Skin-picking
- Small hand
- Small pituitary gland
- Small scrotum
- Specific learning disability
- Strabismus
- Ventriculomegaly
- Weak cry
Sometimes5–29%
26- Abnormal rapid eye movement sleep
- Almond-shaped palpebral fissure
- Central hypothyroidism
- Central sleep apnea
- Chorioretinal hypopigmentation
- Confusional arousal
- Downturned corners of mouth
- Hip dysplasia
and 18 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.
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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