Definition

Macrognathia is a condition where the jaw is abnormally large. It often occurs as a symptom of other medical conditions such as gigantism, pituitary gland tumors, and genetic disorders. The cause may be genetic or due to an underlying health issue.

While some individuals with macrognathia may not experience significant difficulties, others might face challenges related to speaking, eating, and breathing. Surgical procedures can often correct the condition. Macrognathia is also referred to as prognathism, which describes a protruding jaw.

Types of macrognathia include:

1. Mandibular macrognathia: Enlarged lower jaw (mandible), leading to mandibular prognathism, where the jaw extends outward more than usual.
2. Maxillary macrognathia: Enlarged upper jaw (maxilla), resulting in maxillary or alveolar prognathism, where the upper jaw protrudes outward.
3. Bimaxillary macrognathia: Both upper and lower jaws are enlarged, causing the upper and lower jaws to protrude more than normal.

Causes

Several conditions can lead to macrognathia, including:

• Genetic Factors

Some people are born with bigger jaw sizes. In some cases, macrognathia is inherited and not linked to other health problems.

• Acromegaly

This rare condition is caused by an overproduction of growth hormone, often caused by a pituitary gland tumor. Excess of hormones caused the enlargement of tissues, including the jaw. This leads to an enlarged lower jaw (mandible). This is a rare condition with an incidence of 60 people in 1 million.

• Basal Cell Nevus Syndrome

A rare inherited disorder causing facial abnormalities such as a larger jaw, wide-set eyes, abnormal nose width, unusual eyebrow shape and facial features. The incidence of this syndrome is quite rare and affects 1 in 31,000 people.

• Other Genetic Diseases

Conditions like Down syndrome and Crouzon syndrome, both genetic in origin, can lead to excessive jaw growth due to abnormal bone development. In Crouzon syndrome there is premature fusion of the skull bones and in Down syndrome there is an extra chromosome (on chromosome 21) which affects body formation.

Risk Factor

Macrognathia can be congenital or develop as part of another medical condition. Factors increasing the risk include:

• Family History: Genetic inheritance can play a role in some cases of macrognathia.
• Underlying Medical Conditions: Some conditions can raise the likelihood of developing macrognathia, such as:
  • Acromegaly
  • Basal cell nevus syndrome
  • Down syndrome
  • Crouzon syndrome 

Symptoms

The symptoms of macrognathia vary and may include:

• Protruding jaws, either the upper, lower, or both jaws may protrude.
• Malocclusion between the upper and lower teeth, affecting the bite.
• Difficulty speaking, where jaw abnormalities can interfere with normal speech.
• Eating and chewing issues, an enlarged jaw can complicate food intake.
• The condition can impact the airway in severe cases.

Macrognathia is often a sign of a more complex syndrome or medical condition. Other associated symptoms should also be monitored to better understand the underlying cause.

Diagnosis

Diagnosing macrognathia involves a comprehensive medical interview where the doctor inquires about your or your child's symptoms, such as challenges with speaking, chewing, or biting, and other relevant symptoms. The doctor will also ask about potential risk factors, such as family history of genetic conditions or macrognathia, as well as history during pregnancy.

A physical examination of the face will follow, focusing on the upper and lower jaws. Additional diagnostic tests may be suggested to confirm the diagnosis, such as:

• Skull X-rays (panoramic radiography and cephalometry)
• Dental X-rays
• Bite impressions to create a model of your teeth structure

Management

In some cases, macrognathia does not cause significant functional issues, and treatment may primarily address facial aesthetics. However, when macrognathia affects daily activities like eating, speaking, or breathing, treatment options include:

• Orthognathic Surgery
  

Consulting with an oral and facial surgeon can help correct the jaw's structure and facial appearance. Surgery involves removing and repositioning parts of the jawbone. Braces may be needed before and after surgery to help align teeth with the new jaw position.

The recovery period after corrective jaw surgery typically lasts 9 to 12 months. During the first six weeks, a modified diet is necessary to allow the jaw to heal. 

Most patients can resume their daily activities after 2 to 3 weeks. Pain relief medications may also be prescribed during recovery.

• Orthodontic Dental Care
  

Orthodontic treatment, often in collaboration with an oral surgeon, can improve the alignment of the jaw and teeth. Treatment with braces or other dental appliances may be necessary depending on the case.

Since macrognathia may be related to another medical condition, managing the underlying disease is also important.

Complications

Macrognathia can lead to malocclusion, which is an improper alignment between the upper and lower teeth. Common types of malocclusion include:

• Overbite: When the upper jaw teeth overlap the lower jaw teeth during biting. Overbite complications may include:
• Structural issues in the teeth, especially if lower front teeth grow excessively upward.
• Faster tooth damage and loss of structure in the lower front teeth.
• Painful sores, especially in severe cases, where the lower teeth touch the roof of the mouth.
• Difficulty in eating and speaking clearly.

• Underbite: When the lower jaw teeth are positioned in front of the upper jaw teeth during biting. If left untreated, underbite can put excessive stress on the jaw joints, potentially damaging the teeth and jaw.

Other complications arising from malocclusion may include:

• Trouble chewing food
• Difficulty properly cleaning the teeth
• Increased risk of tooth decay, cavities, and gum disease
• Excessive pressure on the teeth, jaw, and surrounding muscles

Prevention

There is no known method to prevent macrognathia, particularly when it is due to genetic factors or hereditary diseases. However, if you are planning to have children and are concerned about passing on genetic conditions, you can consult a genetic counselor. This can help you understand and manage the risks of transmitting such conditions.

When to See a Doctor?

Some individuals are born with macrognathia, and it may not affect their daily life. However, if you experience difficulties with eating, speaking, or breathing due to an enlarged jaw, consult your doctor to explore treatment options. If macrognathia is related to another disease, it is essential to seek medical attention to address the underlying cause.

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