Overview
Humeral agenesis or hypoplasia (unilateral) is a very rare congenital condition in which one of the two upper arm bones (the humerus) is either completely absent (agenesis) or significantly underdeveloped (hypoplasia) on one side of the body. This condition is present at birth and is typically noticed immediately because one arm appears much shorter than the other or is missing a significant portion of its structure. The humerus is the long bone that connects the shoulder to the elbow, so when it is absent or small, the affected arm may have limited length, reduced range of motion, and decreased strength. It is important to note that this specific Orphanet entry (295061) is marked as OBSOLETE, meaning it has been retired or merged into a broader classification of limb reduction defects or upper limb anomalies. Patients with this finding may now be classified under more comprehensive categories of congenital limb deficiencies. The condition can occur in isolation or as part of a broader syndrome involving other skeletal or organ abnormalities. Treatment is primarily supportive and may include prosthetic devices, physical therapy, occupational therapy, and in some cases reconstructive or orthopedic surgery. The goal of treatment is to maximize function, independence, and quality of life. Early intervention with adaptive devices and therapy can help children reach important developmental milestones. The long-term outlook depends on whether the condition is isolated or part of a larger syndrome.
Also known as:
Key symptoms:
One arm significantly shorter than the otherAbsent or underdeveloped upper arm bone on one sideLimited movement of the affected armReduced grip strength on the affected sideDifficulty with tasks requiring two handsAsymmetry of the shouldersPossible abnormalities of the elbow or shoulder jointReduced muscle mass in the affected armPossible associated hand or forearm abnormalities on the same side
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: Humeral agenesis/hypoplasia, unilateral.
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Specialists
View all specialists →No specialists are currently listed for OBSOLETE: Humeral agenesis/hypoplasia, 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: Humeral agenesis/hypoplasia, 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
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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.Is this condition isolated or could it be part of a broader syndrome?,Should genetic testing be performed, and what would it involve?,When should my child be fitted for a prosthetic device?,What types of therapy are recommended and how often?,Are there any surgical options that could improve arm function?,What school accommodations should we request?,Is there a risk of this condition occurring in future children?
Common questions about OBSOLETE: Humeral agenesis/hypoplasia, unilateral
What is OBSOLETE: Humeral agenesis/hypoplasia, unilateral?
Humeral agenesis or hypoplasia (unilateral) is a very rare congenital condition in which one of the two upper arm bones (the humerus) is either completely absent (agenesis) or significantly underdeveloped (hypoplasia) on one side of the body. This condition is present at birth and is typically noticed immediately because one arm appears much shorter than the other or is missing a significant portion of its structure. The humerus is the long bone that connects the shoulder to the elbow, so when it is absent or small, the affected arm may have limited length, reduced range of motion, and decreas
At what age does OBSOLETE: Humeral agenesis/hypoplasia, unilateral typically begin?
Typical onset of OBSOLETE: Humeral agenesis/hypoplasia, unilateral is neonatal. Age of onset can vary across affected individuals.