What Is Micrognathia?
Micrognathia refers to having a very small lower jaw. A child with micrognathia has a lower jaw that is much shorter than the rest of his or her face.
Children may be born with this problem, or it can occur later on. It mainly occurs in children who are born with certain genetic conditions, such as Trisomy 13 and progeria. It can also be caused by fetal alcohol syndrome.
In some cases, this problem goes away as the child’s jaw grows with age. In severe cases, micrognathia can cause feeding problems. It can also lead to malocclusion of the teeth, which means that your child’s teeth aren’t aligned correctly.
Underlying Causes of Micrognathia
Some cases of micrognathia are caused by inherited disorders. In other cases, the problem is caused by genetic mutations that aren’t passed down through families. Conditions that often cause a shortened lower jaw include:
Pierre Robin Syndrome
This condition causes your baby’s jaw to form slowly in the womb, which results in a very small lower jaw. It also causes the baby’s tongue to fall backward into the throat, which can block the airways and make breathing difficult.
Trisomies 13 and 18
Trisomies are genetic disorders that occur when babies have extra genetic material. They cause severe mental deficiencies and physical deformities. About one in every 16,000 babies has trisomy 13, according to the National Institutes of Health (NIH, 2012). Around one in every 5,000 babies (not including those who are stillborn) has trisomy 18 (NIH, 2012). The number refers to which chromosome the extra material comes from.
This is a rare inherited disorder in which your child’s pituitary gland doesn’t make enough growth hormone. This causes severe bone problems, including a small lower jaw, a narrow chest, and unusually short legs, arms, neck, and torso.
This genetic condition causes your child to age at a rapid rate. Babies typically look fine when they’re born, but start showing signs of the disorder by the end of their first year. It is caused by a genetic mutation, but it’s not passed down through families. In addition to a small jaw, your child may also have a slow growth rate, hair loss, and a very narrow face.
This is a rare genetic condition that causes developmental disabilities and physical deformities, including a small jaw and low-set ears. It is named after the high-pitched, cat-like cry that babies with this condition make. It is usually not inherited.
Treacher Collins Syndrome
This hereditary condition causes severe facial abnormalities. In addition to a small jaw, it can also cause a cleft palate, absent cheekbones, and malformed ears. It’s caused by treacle, which is defective protein. According to the NIH, this condition occurs in about one in every 50,000 people (NIH, 2012).
When to See a Doctor
Call your child’s doctor if your child’s jaw looks unusually small or if your baby is having trouble eating. Some of the genetic conditions that cause a small lower jaw are serious and should be diagnosed as soon as possible so that treatment can begin.
Let your child’s doctor or dentist know if your child has trouble chewing, biting, or talking. Problems like these can be a sign of misaligned teeth, which can be fixed by an orthodontist or oral surgeon.
Your child’s lower jaw may grow long enough on its own, especially during puberty. In this case, no treatment is required.
In general, treatments for micrognathia include:
- modified eating methods and special equipment if your child is having trouble eating. Your doctor can help you find a local hospital that offers classes on this subject
- corrective surgery performed by an oral surgeon. The surgeon will add or move pieces of bone to extend your child’s lower jaw
- corrective devices, such as braces, to fix misaligned teeth caused by having a short jaw
Specific treatments for your child’s underlying condition depend on what the condition is, which symptoms it is causing, and how severe it is. Treatment methods can range from medications and close monitoring to major surgery and supportive care.
What to Expect
If your child’s jaw grows longer on its own, feeding problems usually stop.
Corrective surgery is generally successful, but it can take nine to 12 months for your child’s jaw to heal.
Ultimately, the outlook depends on the condition that caused micrognathia. Babies with certain conditions, such as achondrogenesis or trisomy 13, only live for a short time. Children with conditions such as Pierre Robin syndrome or Treacher Collins syndrome are able to live relatively normal lives with or without treatment. Your child’s doctor can let you know what the outlook is based on your child’s specific condition.
There’s no direct way to prevent micrognathia, and many of the underlying conditions that cause it can’t be prevented either. If you have an inherited disorder, a genetic counselor can tell you how likely you are to pass it on to your child.