Overview
Jansen type metaphyseal chondrodysplasia (also called Jansen's metaphyseal chondrodysplasia or Jansen disease) is an extremely rare genetic disorder that affects how bones grow and develop. It belongs to a group of conditions called skeletal dysplasias, which means the bones form and grow in an unusual way. The disease is caused by a change (mutation) in a gene called PTH1R, which controls how the body responds to parathyroid hormone — a hormone that normally helps regulate calcium and phosphate levels in the blood and bones. People with this condition have bones that do not develop properly at the growth plates — the areas near the ends of long bones where new bone tissue is made. This leads to short stature, bowed legs, and joints that look enlarged or knobby. The face may also look different, with a small jaw and wide-set eyes. Interestingly, blood calcium levels are often very high even though parathyroid hormone levels are normal or low, which can cause additional health problems. There is currently no cure for Jansen type metaphyseal chondrodysplasia. Treatment focuses on managing symptoms, especially high calcium levels (hypercalcemia), bone pain, and mobility challenges. A team of specialists including endocrinologists, orthopedic surgeons, and clinical geneticists typically work together to support affected individuals throughout their lives.
Key symptoms:
Very short stature (much shorter than average height)Bowed legs and armsEnlarged, knobby-looking jointsHigh calcium levels in the blood (hypercalcemia)Low phosphate levels in the bloodBone pain or tendernessWaddling walk or difficulty walkingDistinctive facial features such as wide-set eyes, a small jaw, and a high foreheadHearing loss in some casesKidney stones (from high calcium levels)Muscle weaknessDental problems including delayed or abnormal tooth developmentShortened fingers and toes
Clinical phenotype terms (25)— hover any for plain English
Autosomal dominant
Passed on from just one parent; each child has about a 50% chance of inheriting it
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for Metaphyseal chondrodysplasia, Jansen type.
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Specialists
View all specialists →No specialists are currently listed for Metaphyseal chondrodysplasia, Jansen type.
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 Metaphyseal chondrodysplasia, Jansen type.
Community
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Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
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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.What calcium level is safe for my child, and how often should we check it?,Are there any medications or supplements (like vitamin D or calcium) that we should avoid?,Does my child need orthopedic surgery now, or can we wait and monitor?,What signs should prompt us to go to the emergency room?,Should other family members be tested for the PTH1R gene mutation?,Are there any clinical trials or research studies we could participate in?,What support services or patient organizations can help our family?
Common questions about Metaphyseal chondrodysplasia, Jansen type
What is Metaphyseal chondrodysplasia, Jansen type?
Jansen type metaphyseal chondrodysplasia (also called Jansen's metaphyseal chondrodysplasia or Jansen disease) is an extremely rare genetic disorder that affects how bones grow and develop. It belongs to a group of conditions called skeletal dysplasias, which means the bones form and grow in an unusual way. The disease is caused by a change (mutation) in a gene called PTH1R, which controls how the body responds to parathyroid hormone — a hormone that normally helps regulate calcium and phosphate levels in the blood and bones. People with this condition have bones that do not develop properly
How is Metaphyseal chondrodysplasia, Jansen type inherited?
Metaphyseal chondrodysplasia, Jansen type follows a autosomal dominant inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Metaphyseal chondrodysplasia, Jansen type typically begin?
Typical onset of Metaphyseal chondrodysplasia, Jansen type is neonatal. Age of onset can vary across affected individuals.