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Micrognathia (Small Lower Jaw) - Causes, Symptoms, Diagnosis, and Treatment

Published on Jan 11, 2021 and last reviewed on Sep 23, 2022   -  5 min read


Micrognathia (small jaw or mandibular hypoplasia) is when a child is born with or develops a smaller than normal lower jaw. Read about its causes, diagnosis, and treatment.


What Does Micrognathia Mean?

Micrognathia, otherwise called small jaw or mandibular hypoplasia, is when a child is born with or develops a smaller than normal lower jaw or mandible. The lower jaw of such a child is much shorter and smaller as compared to the rest of the face. It can be seen at birth or develop later in life. Micrognathia is associated with various syndromes, such as fetal alcohol syndrome, Pierre Robin syndrome, Treacher Collins syndrome, hemifacial microsomia, Stickler syndrome, etc., and genetic conditions like progeria and trisomy 13 and 18. Sometimes, the jaw grows with age, and the problem goes away, but in severe cases, micrognathia can lead to feeding problems, breathing difficulties, and malocclusion (misaligned teeth), as there is not enough space for all the teeth to grow in the small jaw.

Infants with micrognathia may need special nipples and have to be appropriately positioned to feed properly and to prevent cyanosis due to breathing problems. Prognosis depends on how small the jaw is, but outcomes are generally good.

What Are the Causes of Micrognathia?

People with a small jaw are usually born that way. In a few cases, genetic disorders are the cause, and in some, spontaneous genetic mutations are to blame. The following hereditary syndromes have micrognathia as a symptom:

The other syndromes that can result in micrognathia are Marfan syndrome, Möbius syndrome, Prader-Willi syndrome, Silver-Russell syndrome, Wolf-Hirschhorn syndrome, Turner syndrome, etc.

What Are the Symptoms Associated With Micrognathia?

Children with micrognathia often show the following signs and symptoms:

When to Consult a Doctor for Micrognathia?

If your newborn’s jaw looks extremely small or if he or she is having trouble feeding, consult a doctor immediately. As some syndromes and genetic conditions associated with micrognathia are serious, prompt diagnosis and treatment are essential. Sometimes, your doctor might diagnose micrognathia before birth with an ultrasound.

How Does a Doctor Diagnose Micrognathia?

A small lower jaw can be clearly seen when its length is compared to the upper jaw. Once the doctor sees a discrepancy in the mandible size, he or she will conduct a physical examination to look for cleft palate, facial asymmetries, and tongue tie. If needed, the doctor will then order X-rays or a CT scan to define the anatomy of the face and head. A polysomnogram or sleep study might be needed to measure the child’s breathing, oxygenation during sleep, and brain and heart function.

How Is Micrognathia Treated?

The treatment options for micrognathia include:

1) Non-surgical Treatment -

2) Surgical Treatment -

The prognosis for children with micrognathia is generally good, but it can vary based on the severity. Quick diagnosis and treatment, including surgeries, are essential to give the child the best long-term quality of life. The treatment plan will depend on the child’s jaw growth and development. For more information, consult a doctor online now.


Frequently Asked Questions


Why Is My Lower Jaw Small?

Children with a small lower jaw or micrognathia can either be born with it or develop it later in their life. It occurs either due to genetic syndromes, mutations or can be inherited. Such syndromes and conditions causing micrognathia include,
- Progeria.
- Treacher Collins syndrome.
- Pierre Robin syndrome.
- Trisomy 13.
- Trisomy 18.
- Cri-du-chat syndrome.
- Achondrogenesis.
- Skeletal and neuromuscular diseases.
- Fetal alcohol syndrome.


What Symptoms are Micrognathia Associated With?

Below are some conditions exhibited in people or children with micrognathia.
- Breathing difficulties.
- Feeding difficulties.
- Obstructive sleep apnea (temporary stop of breathing during sleep).
- Sleeping difficulties.
- Excessive breathing sounds.
- Malaligned and crowded lower teeth.


Is It Common To Have a Small Lower Jaw?

Micrognathia is common in infants and gets self-corrected with the baby’s growth. However, it is uncommon to persist in adulthood. Children with syndromes like progeria, Down’s syndrome, achondroplasia, etc., more commonly are born with small lower jaws that prevail even in their adulthood.


Can a Pregnancy Ultrasound Scan Detect Micrognathia?

Pregnancy ultrasound scans can reveal micrognathia. Ultrasound scans, especially 3-D scans performed at the 10th week of pregnancy, can reveal any abnormalities in the shape and size of the jaws if the baby’s head is positioned favorably. Apart from this, the jaw sizes can also be estimated by measuring the same in the ultrasound images.


What Do You Mean by Fetal Micrognathia?

A prenatal ultrasound scan or scan of a 10-week old pregnant woman reveals any problems with jaw development. Lower jaw deficiency in the growing fetus within the womb is known as fetal micrognathia. This may be due to syndromes and chromosomal abnormalities hindering normal fetal jaw development.


Trisomy of Which Chromosomes Leads to Micrognathia?

Trisomy of the 13th and 18th chromosomes leads to Patau syndrome and Edwards syndrome presenting micrognathia as one of their features.


Is It Not Good to Have a Small Lower Jaw?

A lower jaw smaller than usual does affect the facial appearance, breathing, eating, chewing, speech, and temporomandibular joint (jaw joint) and cause ill health effects.


Will a Small Lower Jaw Get Corrected by Itself?

Small lower jaws in newborns eventually get corrected on their own with babies’ growth. In some conditions, if it fails to get corrected even after all permanent teeth have erupted, supportive non-surgical methods and jaw reconstruction and enlargement surgeries like mandibular distraction osteogenesis help.


How to Non-Surgically Correct a Small Lower Jaw?

There are no non-surgical ways to correct a deficient lower jaw. However, non-surgical options like changing sleeping positions (lying on the stomach) and nasopharyngeal tubes can help maintain the airway and lead a comfortable life.


What Ways Help Me Increase the Size of My Lower Jaw?

To increase the size of the lower jaw, surgical options are the only available methods. They include,
- Chin implants.
- Sliding genioplasty.
Though both the above mentioned procedures do not actually increase the jaw’s size, they help give a normal-sized lower jaw look; below mentioned is the jaw lengthening surgical procedure.
Mandibular distraction osteogenesis.


What Complications Do Small Lower Jaws Cause?

Micrognathia can lead to
- Troubled eating.
- Difficulty speech.
- Breathing difficulties.
- Disrupted sleep.
- Mild facial deformity.

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Last reviewed at:
23 Sep 2022  -  5 min read


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