Overview
Isolated humeral agenesis or hypoplasia is a very rare birth defect in which the humerus — the long bone of the upper arm — is either completely absent (agenesis) or abnormally short and underdeveloped (hypoplasia). The word 'isolated' means this bone problem occurs on its own, without other major birth defects or a recognized genetic syndrome. The condition can affect one arm (unilateral) or both arms (bilateral), and the severity varies widely. In mild cases, the upper arm bone may simply be shorter than normal, while in severe cases it may be almost entirely missing, causing the forearm and hand to sit very close to the shoulder. Because the humerus plays a central role in arm movement, children born with this condition often have significant limitations in reaching, lifting, and performing everyday tasks with the affected arm. The elbow joint may be absent or malformed, and surrounding muscles and nerves may also be underdeveloped. Despite these challenges, many children adapt remarkably well, especially with early intervention. There is no cure that can regrow or fully replace the missing bone. Treatment focuses on maximizing function through physical therapy, occupational therapy, and sometimes prosthetic devices or surgical procedures such as limb lengthening. A team of specialists typically works together to support the child's development and independence. Outcomes depend on the severity of the bone deficiency and whether one or both arms are involved.
Also known as:
Key symptoms:
Shortened or absent upper arm boneVisibly shorter arm on one or both sidesLimited ability to bend or straighten the elbowDifficulty reaching overheadReduced grip strength on the affected sideAbnormal shape or appearance of the upper armLimited range of motion in the shoulderAbsent or malformed elbow jointForearm appearing to attach near the shoulder in severe casesMuscle underdevelopment in the affected armDifficulty with daily tasks like dressing or feeding
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 Isolated humeral agenesis/hypoplasia.
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Specialists
View all specialists →No specialists are currently listed for Isolated humeral agenesis/hypoplasia.
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 Isolated humeral agenesis/hypoplasia.
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 my child's condition, and is one or both arms affected?,Are there any other birth defects or syndromes we should test for?,Would genetic testing help us understand the cause or risk for future children?,What types of therapy should we start, and how soon?,Is my child a candidate for prosthetic devices, and when should we begin fitting?,Are there surgical options like limb lengthening that might help?,What school accommodations should we request as my child grows?
Common questions about Isolated humeral agenesis/hypoplasia
What is Isolated humeral agenesis/hypoplasia?
Isolated humeral agenesis or hypoplasia is a very rare birth defect in which the humerus — the long bone of the upper arm — is either completely absent (agenesis) or abnormally short and underdeveloped (hypoplasia). The word 'isolated' means this bone problem occurs on its own, without other major birth defects or a recognized genetic syndrome. The condition can affect one arm (unilateral) or both arms (bilateral), and the severity varies widely. In mild cases, the upper arm bone may simply be shorter than normal, while in severe cases it may be almost entirely missing, causing the forearm and
At what age does Isolated humeral agenesis/hypoplasia typically begin?
Typical onset of Isolated humeral agenesis/hypoplasia is neonatal. Age of onset can vary across affected individuals.