Overview
Humero-radio-ulnar synostosis (unilateral) is a rare bone condition in which two or more of the bones in the arm — the humerus (upper arm bone), radius, and ulna (the two forearm bones) — are fused together on one side of the body. This fusion happens during early development before birth, meaning the bones never fully separate as they normally would. The term 'OBSOLETE' in the official name means this specific classification is no longer actively used in the Orphanet rare disease database, and the condition may now be grouped under a broader category of limb bone fusions (synostoses). People with this condition typically have limited movement in the affected elbow or forearm. They may not be able to fully bend, straighten, or rotate the arm. The degree of limitation depends on how much of the bones are fused. In many cases, the condition is noticed at birth or in early childhood when the child has difficulty with arm movements. Treatment is generally focused on managing symptoms and improving function. Physical therapy and occupational therapy can help maximize the use of the affected arm. In some cases, surgery may be considered to improve the position of the arm or attempt to restore some movement, though results vary. Because this is a structural bone problem present from birth, there is no medication that can reverse the fusion. Many individuals adapt well and lead full, active lives with appropriate support.
Also known as:
Key symptoms:
Limited ability to bend or straighten the elbowInability to rotate the forearm (turn palm up or down)Stiffness in the affected armReduced range of motion in the elbow jointDifficulty with daily tasks like eating or dressing on the affected sideVisible difference in arm position or postureArm may be fixed in one positionPossible shortening of the affected armDifficulty carrying objects with the affected arm
Variable
Can be inherited in different ways depending on the underlying gene
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for OBSOLETE: Humero-radio-ulnar synostosis, unilateral.
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Specialists
View all specialists →No specialists are currently listed for OBSOLETE: Humero-radio-ulnar synostosis, unilateral.
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 OBSOLETE: Humero-radio-ulnar synostosis, unilateral.
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 severe is the bone fusion, and which bones are involved?,Is this an isolated finding, or could it be part of a genetic syndrome?,Should my child have genetic testing?,Would surgery be helpful in this case, and what are the risks?,What types of therapy would benefit my child the most?,Are there adaptive devices that could help with daily activities?,How should we monitor this condition as my child grows?
Common questions about OBSOLETE: Humero-radio-ulnar synostosis, unilateral
What is OBSOLETE: Humero-radio-ulnar synostosis, unilateral?
Humero-radio-ulnar synostosis (unilateral) is a rare bone condition in which two or more of the bones in the arm — the humerus (upper arm bone), radius, and ulna (the two forearm bones) — are fused together on one side of the body. This fusion happens during early development before birth, meaning the bones never fully separate as they normally would. The term 'OBSOLETE' in the official name means this specific classification is no longer actively used in the Orphanet rare disease database, and the condition may now be grouped under a broader category of limb bone fusions (synostoses). People
At what age does OBSOLETE: Humero-radio-ulnar synostosis, unilateral typically begin?
Typical onset of OBSOLETE: Humero-radio-ulnar synostosis, unilateral is neonatal. Age of onset can vary across affected individuals.