Overview
SIM1-related Prader-Willi-like syndrome is a rare genetic condition caused by changes (mutations) in the SIM1 gene. It is sometimes called SIM1 deficiency or SIM1-related obesity syndrome. This condition shares many features with Prader-Willi syndrome but has a different genetic cause. The SIM1 gene plays an important role in brain development, particularly in the hypothalamus — the part of the brain that controls hunger, body weight, and certain hormones. People with this condition typically develop severe obesity beginning in early childhood due to an overwhelming and constant feeling of hunger (called hyperphagia). Other common features can include mild to moderate intellectual disability, behavioral challenges, low muscle tone (hypotonia) in infancy, and some features that overlap with autism spectrum disorder. Some individuals may also have hormonal imbalances and delayed development. There is currently no cure for SIM1-related Prader-Willi-like syndrome. Treatment focuses on managing symptoms, especially controlling weight through strict dietary supervision, behavioral strategies, and regular physical activity. Hormonal deficiencies, if present, may be treated with replacement therapy. Early intervention services, including speech therapy, occupational therapy, and behavioral support, can help improve developmental outcomes. A team of specialists working together provides the best care for affected individuals.
Also known as:
Key symptoms:
Severe early-onset obesityConstant and extreme hunger (hyperphagia)Low muscle tone in infancyMild to moderate intellectual disabilityDelayed speech and language developmentBehavioral problems such as tantrums or stubbornnessFeatures resembling autism spectrum disorderDelayed motor milestones like sitting and walkingHormonal imbalancesShort stature in some casesDifficulty with learning and memorySleep problemsSmall hands and feet in some individuals
Clinical phenotype terms (50)— hover any for plain English
Autosomal dominant
Passed on from just one parent; each child has about a 50% chance of inheriting it
Infantile
Begins in infancy, roughly 1 month to 2 years old
Treatments
No FDA-approved treatments are currently listed for SIM1-related Prader-Willi-like syndrome.
View clinical trials →Clinical Trials
View all trials with filters →No actively recruiting trials found for SIM1-related Prader-Willi-like syndrome at this time.
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Specialists
View all specialists →No specialists are currently listed for SIM1-related Prader-Willi-like syndrome.
Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to SIM1-related Prader-Willi-like syndrome.
Community
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Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.How can we best manage my child's hunger and prevent dangerous weight gain?,Should my child be tested for growth hormone deficiency or other hormonal problems?,Is setmelanotide or any other medication appropriate for my child's specific genetic change?,What early intervention therapies do you recommend, and how often should they occur?,Are there clinical trials or research studies my child could participate in?,What screening tests should be done regularly to watch for obesity-related complications?,Should other family members be tested for the SIM1 gene change?
Common questions about SIM1-related Prader-Willi-like syndrome
What is SIM1-related Prader-Willi-like syndrome?
SIM1-related Prader-Willi-like syndrome is a rare genetic condition caused by changes (mutations) in the SIM1 gene. It is sometimes called SIM1 deficiency or SIM1-related obesity syndrome. This condition shares many features with Prader-Willi syndrome but has a different genetic cause. The SIM1 gene plays an important role in brain development, particularly in the hypothalamus — the part of the brain that controls hunger, body weight, and certain hormones. People with this condition typically develop severe obesity beginning in early childhood due to an overwhelming and constant feeling of hu
How is SIM1-related Prader-Willi-like syndrome inherited?
SIM1-related Prader-Willi-like syndrome follows a autosomal dominant inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does SIM1-related Prader-Willi-like syndrome typically begin?
Typical onset of SIM1-related Prader-Willi-like syndrome is infantile. Age of onset can vary across affected individuals.