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Absent Depressor Anguli Oris Muscle (ADAOM) is a congenital (present at birth) condition involving the muscle that normally pulls down the corner of the mouth.
🧬 What is it?
The depressor anguli oris muscle controls downward movement of the mouth corners (like when frowning).
If it’s absent or underdeveloped on one side:
The face looks symmetrical at rest
When crying or smiling, one side of the mouth doesn’t move downward, causing asymmetry
This is often called asymmetric crying facies.
🧬 Genetics & Causes
ADAOM can occur:
1. Isolated (most common)
No clear genetic mutation identified
Likely due to developmental disruption during fetal growth
Usually sporadic (not inherited)
2. Associated with Genetic Syndromes
In some cases, ADAOM is linked to chromosomal abnormalities, especially:
22q11.2 deletion syndrome
One of the most important associations
Caused by a microdeletion on chromosome 22
Inheritance: autosomal dominant, but often de novo (new mutation)
Other possible associations:
Cardiac defects (e.g., ventricular septal defect)
Craniofacial anomalies
🧬 Inheritance Pattern
Most cases → sporadic (non-inherited)
If part of a syndrome like 22q11.2 deletion:
Can be autosomal dominant
~50% chance of passing it on if a parent carries the deletion
🧬 Clinical Importance
Doctors may investigate further because ADAOM can be a marker for underlying conditions, especially:
Congenital heart disease
Chromosomal abnormalities
🧬 Diagnosis
Clinical observation (facial asymmetry when crying)
If suspected syndrome:
Genetic testing (e.g., FISH or microarray for 22q11.2 deletion)
Cardiac evaluation
🧬 Management
Isolated ADAOM → usually no treatment needed
Cosmetic concerns → sometimes surgical correction later in life
If syndromic → manage associated conditions
🧠 Key Takeaway
ADAOM is usually benign and sporadic
But it can be a clinical clue to genetic syndromes, especially 22q11.2 deletion
If you want, I can go deeper into embryology, facial nerve vs muscle differentiation, or how to distinguish it from facial nerve palsy—those are common exam topics.
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