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Macrognathia and Micrognathia: What are they?

Macrognathia and micrognathia are conditions where the jaws are much larger or smaller than the rest of the face. They are problems that usually are not painful. They can be fixed with surgery. However, other options are also available.

They are the result of some genetic disorders. Since they may adjust to the face’s size as the body ages, many dentists believe it is ok to wait until one is an adult before planning any surgical treatment.

What is Macrognathia?

Macrognathia means the lower jawbone is larger than the upper jawbone. The condition can be described thus:

  • The lower jaw can be in the wrong position
  • The teeth can become very large
  • When smiling, the upper gum line is more exposed than it should be
  • The chin may appear larger than the individual’s other facial features
  • You cannot see the upper teeth when someone speaks or smiles.

What is Micrognathia?

Micrognathia is the opposite of macrognathia. When someone has a smaller lower jaw than an upper jaw, they have macrognathia. It is sometimes referred to as ‘strawberry face.’

Most cases of micrognathia are found in infants. It is a problem that mothers first notice. They see this when the infant has difficulty feeding.

This condition can have the following symptoms:

  • The chin is behind the upper jaw
  • Signs of apnea or breathing problems in newborn babies
  • Rapid breathing or increased breathing rate

What Causes Macrognathia and Micrognathia?

Causes of Macrognathia

A common cause of macrognathia is the use of forceps during birth. This happens when the baby is pulled out with a pair of forceps. Using forceps during childbirth is rarer than it used to be. Today, forceps are used in only about 1% of births.

Other causes of macrognathia may include:

  • Trauma – such as injuries to the face
  • Inheritance – macrognathia can also be inherited
  • Side-effects – macrognathia may be a side-effect of another syndrome

Causes of Micrognathia

A common cause of micrognathia is a genetic mutation. Parents can pass down the condition to their children.

It can happen at birth but also later in life. It may make feeding children difficult. In addition, it may cause breathing difficulty in them.

Another reason may be Down’s Syndrome. The child is born with an extra copy of chromosome 21.

Other causes of micrognathia may include:

  • Early birth
  • Cleft lip or palate
  • Fetal Alcohol Syndrome
  • Other defects or syndromes

Other Causes

Macrognathia and micrognathia can also be the result of the following:

  • Bird-headed dwarfism. Also clalled Seckel Syndrome. A child can have this condition when they lack ATR protein. ATR is an enzyme whose job is to see if any damage in DNA. Children with Seckel Syndrome will have narrow bird-like faces with beak-like noses.
  • Hutchinson-Gilford syndrome. Children with this syndrome age faster than usual. They often have shallow and recessed jaws.
  • Hanhart syndrome. This is a birth defect that may result from genetic and environmental factors. Children with this syndrome may have unusual growth and distinct facial features, such as micrognathia.
  • Edwards syndrome. Babies with this syndrome may be born with a small head and jaw.
  • The abnormal difference in body structure. It is the result of one or more genetic disorders that can affect the growth of limbs. One such disorder is Stickler Syndrome, which causes a small chin in babies.

What are the Symptoms of Macrognathia and Micrognathia?

The bone is a part of the skeleton. It is made of calcium. Ailments that change the balance of calcium in the body can affect bones similarly. If someone has macrognathia or micrognathia, a dentist may refer them to a doctor. This is to see whether the person is suffering from calcium imbalances.

Symptoms of macrognathia and micrognathia include the following:

  • Abnormal or improper growth of the tongue
  • Abnormal position of the tongue. Having a small jaw also prevents the tongue from being held in a forward position
  • Speech disorder
  • Respiratory problems. A shorter tongue is more likely to block airways, causing respiratory problems
  • Feeding difficulty.
  • Irregular alignment of the teeth. Micrognathia stops the teeth from having enough room to grow
  • Malnourishment and growth defects.

What are the treatments for Macrognathia and Micrognathia?

Monitoring the Condition

Macrognathia and micrognathia often correct themselves. The jaw grows quite a bit during puberty. During this time, the flaw still has a chance to correct itself. Monitoring the child’s growth is crucial in this regard.


Braces are a treatment method that does not require surgery. They can help realign misaligned teeth and control the problem as much as possible. But they cannot disappear the problem, as the smaller jaw remains smaller than the other jaw.


Surgery is the last option in this case. Many people suffering from macrognathia and micrognathia live normal life. Unless there is breathing difficulty, surgery is not required.

A surgical procedure includes slowly extending the smaller jawbone to match the larger one. The smaller jawbone will need to be cut to attach turning devices.

The surgery is called Mandibular Distraction Osteogenesis (MDO). The problem it solves is the Pierre Robin sequence. The surgery takes a few months to complete.

The surgery may come with multiple side effects, including the following:

  • Failure of the surgery requiring a second surgery
  • Infection
  • Nerve damage
  • Tooth injury
  • Thick raised scar
  • Improper bite
  • Improper jawbone connection (temporomandibular joint injury)
  • Change in facial structure.

According to a paper published by the National Library of Medicine, infection is the most common complication of surgery. However, the use of antibiotics can help reduce this risk.

Early Detection

In both macrognathia and micrognathia, early detection is key to managing the condition. Infants should have their normal checkups with their doctor. It may be an early sign of both disorders if you have any issues with feeding your child. Remember to discuss this with your child’s doctor.

Final Word

Macrognathia and Micrognathia are both very common. With close monitoring and checkups, both conditions can be caught early. Often these flaws resolve on their own. If you, your child, or another family member suffers from either macrognathia or micrognathia, seek the advice of an orthodontist.


  • The Toronto Video Atlas of Surgery. ‘Routine Forcep Delivery.’
  • University of Colorado School of Medicine. ‘Micrognathia.’
  • UC Irvine School of Medicine. ‘Mandibular Distraction Osteogenesis.’
  • The Journal of Craniofacial Surgery. ‘Complications of Mandibular Distraction Osteogenesis.’
  • National Library of Medicine. ‘Complications associated with neonatal mandibular distraction osteogenesis in the treatment of Robin sequence.’

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