Overview
Hemifacial myohyperplasia is a rare condition in which the muscles on one side of the face grow larger than normal, causing noticeable asymmetry between the two sides of the face. The term 'myohyperplasia' means abnormal overgrowth of muscle tissue, and 'hemifacial' means it affects one half of the face. This condition is sometimes also referred to as hemifacial muscular hypertrophy or congenital hemifacial hyperplasia. It is classified under congenital facial asymmetry disorders. People with this condition typically notice that one side of the face appears fuller, thicker, or more prominent than the other. The enlargement mainly involves the muscles of the face, such as the masseter (jaw muscle) or other muscles used for chewing and facial expression. This can affect the appearance of the cheek, jaw, or other facial structures on the involved side. In some cases, the teeth, tongue, or soft tissues on the affected side may also be slightly larger. Because this is primarily a cosmetic and structural issue, treatment is usually focused on managing the asymmetry rather than curing an underlying disease process. Options may include surgical reduction of the enlarged muscles, orthodontic treatment if the teeth or jaw alignment is affected, and regular monitoring by specialists. The condition is generally not life-threatening, but the visible facial asymmetry can have significant psychological and social effects, especially in children and adolescents.
Key symptoms:
One side of the face appears larger or fuller than the otherEnlarged jaw muscle (masseter) on one sideFacial asymmetry that may become more noticeable with growthUneven cheek fullnessPossible enlargement of the tongue on the affected sideMisalignment of the teeth or bite (malocclusion)Uneven jawlineThickened soft tissues on one side of the faceDifficulty with chewing if jaw alignment is affectedSelf-consciousness or emotional distress about appearance
Sporadic
Usually appears on its own, not inherited from a parent
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for Hemifacial myohyperplasia.
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Specialists
View all specialists →No specialists are currently listed for Hemifacial myohyperplasia.
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 Hemifacial myohyperplasia.
Community
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Caregiver Resources
NORD Caregiver Resources
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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 is causing the enlargement on one side of my child's face, and have other conditions been ruled out?,How will this condition change as my child grows?,What treatment options are available, and when is the best time to consider surgery?,Are there non-surgical options like Botox injections that could help?,Should my child see a geneticist to rule out related overgrowth syndromes?,What kind of emotional or psychological support do you recommend?,How often should we schedule follow-up visits to monitor the condition?
Common questions about Hemifacial myohyperplasia
What is Hemifacial myohyperplasia?
Hemifacial myohyperplasia is a rare condition in which the muscles on one side of the face grow larger than normal, causing noticeable asymmetry between the two sides of the face. The term 'myohyperplasia' means abnormal overgrowth of muscle tissue, and 'hemifacial' means it affects one half of the face. This condition is sometimes also referred to as hemifacial muscular hypertrophy or congenital hemifacial hyperplasia. It is classified under congenital facial asymmetry disorders. People with this condition typically notice that one side of the face appears fuller, thicker, or more prominent
How is Hemifacial myohyperplasia inherited?
Hemifacial myohyperplasia follows a sporadic inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Hemifacial myohyperplasia typically begin?
Typical onset of Hemifacial myohyperplasia is neonatal. Age of onset can vary across affected individuals.