Overview
Obesity due to prohormone convertase I deficiency (also called PC1 deficiency or PCSK1 deficiency) is a very rare genetic condition caused by changes in the PCSK1 gene. This gene provides instructions for making an enzyme called prohormone convertase 1/3 (PC1/3), which plays a key role in processing hormones throughout the body. When this enzyme does not work properly, the body cannot correctly activate many important hormones, including those that control hunger, blood sugar, and growth. The most noticeable effect of this condition is severe obesity that begins in early infancy or childhood. Babies with PC1 deficiency often have serious digestive problems, including chronic diarrhea and difficulty absorbing nutrients from food. As children grow, they may develop problems with blood sugar regulation (similar to diabetes), low thyroid hormone levels, low cortisol (a stress hormone), and issues with reproductive hormones. Growth can also be affected. There is currently no cure for PC1 deficiency, but symptoms can be managed with hormone replacement therapies and dietary support. A medication called setmelanotide (brand name Imcivree) has been approved by the FDA specifically to treat obesity in people with PCSK1 gene variants, offering a meaningful new option for weight management. Early diagnosis and a team of specialists are very important for improving quality of life.
Also known as:
Key symptoms:
Severe obesity starting in infancy or early childhoodChronic diarrhea and poor absorption of nutrients (malabsorption)Low blood sugar (hypoglycemia) in newborns or infantsExtreme hunger and difficulty feeling fullLow cortisol levels (adrenal insufficiency), which can cause fatigue and poor stress responseLow thyroid hormone levels (hypothyroidism), causing tiredness and slow metabolismDelayed or absent puberty due to low reproductive hormonesShort stature or slow growthHigh levels of insulin in the bloodDiabetes or insulin resistance in some patients
Clinical phenotype terms (18)— hover any for plain English
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Infantile
Begins in infancy, roughly 1 month to 2 years old
Treatments
No FDA-approved treatments are currently listed for Obesity due to prohormone convertase I deficiency.
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Specialists
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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
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Caregiver Resources
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Social Security Disability
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Questions for your doctor
Bring these to your next appointment
- Q1.Which hormone levels should we test regularly, and how often?,Does my child or I need an emergency hydrocortisone injection kit, and how do we use it?,Is setmelanotide (Imcivree) an appropriate treatment option for us, and how do we access it?,What dietary changes will help manage the diarrhea and weight?,Should other family members be tested for the PCSK1 gene change?,What signs of adrenal crisis should prompt us to go to the emergency room immediately?,Are there any clinical trials or research studies we should know about?
Common questions about Obesity due to prohormone convertase I deficiency
What is Obesity due to prohormone convertase I deficiency?
Obesity due to prohormone convertase I deficiency (also called PC1 deficiency or PCSK1 deficiency) is a very rare genetic condition caused by changes in the PCSK1 gene. This gene provides instructions for making an enzyme called prohormone convertase 1/3 (PC1/3), which plays a key role in processing hormones throughout the body. When this enzyme does not work properly, the body cannot correctly activate many important hormones, including those that control hunger, blood sugar, and growth. The most noticeable effect of this condition is severe obesity that begins in early infancy or childhood.
How is Obesity due to prohormone convertase I deficiency inherited?
Obesity due to prohormone convertase I deficiency follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Obesity due to prohormone convertase I deficiency typically begin?
Typical onset of Obesity due to prohormone convertase I deficiency is infantile. Age of onset can vary across affected individuals.