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.
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.
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:
Pierre Robin Syndrome (or Sequence) - In this syndrome, the fetus’s jaw is formed slowly in the uterus, resulting in a comparatively smaller lower jaw. Smaller mandible makes the baby’s tongue fall back into the throat, which can choke the baby and make breathing difficult. Such babies also present with a cleft palate (a split in the roof of the mouth).
Progeria - This genetic disorder makes the affected child age rapidly. The signs of progeria are not obvious at birth, but signs become more apparent in the first couple of years of life. Such children have a small lower jaw, hair loss, and narrow face.
Trisomy 13 - Children born with trisomy 13, otherwise called Patau syndrome, is a chromosomal disorder, where instead of two copies, there are three copies of chromosome 13. Around 1 in 16,000 children are born with trisomy 13. Children born with trisomy 13 have low birth weight, cleft lip or palate, small lower jaw, and a small head.
Trisomy 18 - Babies born with trisomy 18, otherwise called Edwards syndrome, have an extra chromosome 18 (three copies instead of two). About 1 in 6,000 children are born with this chromosomal abnormality, and it is the second most common trisomy syndrome after Down syndrome. Such babies might exhibit cleft palate, micrognathia, heart defects, small head, and deformed feet.
Fetal Alcohol Syndrome - The maternal use of alcohol during pregnancy results in birth defects, such as craniofacial malformation and brain abnormalities. The facial deformities include short eyelid folds, upturned nose, thin upper lip, broad nasal bridge, and small lower jaw.
Hemifacial Microsomia - Otherwise called Goldenhar syndrome, is a condition where one side of the face does not grow normally and is underdeveloped.
Achondrogenesis - It is a rare genetic disorder where the pituitary gland does not make enough growth hormone, which leads to bone problems like a small mandible and narrow chest. Such babies have short legs, neck, arms, and torso.
Cri-du-Chat Syndrome - Otherwise called 5p-syndrome or cat cry syndrome, is also a rare hereditary condition that causes physical deformities and developmental disabilities due to a missing genetic material on chromosome 5.
Treacher Collins Syndrome (TCS) - A hereditary condition that causes serious facial abnormalities, such as a small jaw, cleft palate, ear malformation, and no cheekbones.
Catel-Manzke Syndrome - A rare hereditary disorder that results in abnormalities of the index fingers and characteristics of Pierre Robin syndrome, such as micrognathia and cleft palate.
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.
Children with micrognathia often show the following signs and symptoms:
Failure to thrive - inadequate growth during early childhood.
Infant apnea - temporary cessation of breathing.
Feeding difficulties - the inability to feed, problems with latching, and insufficient weight gain.
Tongue-tie - the tongue is attached to the mandible near the chin.
Glossoptosis - retraction or downward positioned tongue.
Breathing problems - can result in cyanosis, where the baby’s skin or mucous membrane turns blue due to lack of oxygen.
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.
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.
The treatment options for micrognathia include:
1) Non-surgical Treatment -
Make the child sleep in the prone position, on the stomach or chest, as it thrusts the base of the tongue forward and keeps the airway open.
The airway can be kept open with the help of a flexible tube that is inserted into the child’s nasal passage through the nostril.
Pressure ventilators like CPAP (continuous positive airway pressure) or BiPAP (Bi-level positive airway pressure) can be used for sleep apnea.
Orthodontic treatment to correct a malocclusion.
2) Surgical Treatment -
The tongue-tie is removed to allow easy moving of the tongue-base forward to keep the airway open.
The mandible can be slowly lengthened to relieve the airway with mandibular distraction osteogenesis (MDO).
Sometimes, an airway opening must be created in the neck (tracheostomy) to bypass the obstruction caused by a small jaw.
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.
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,
- Treacher Collins syndrome.
- Pierre Robin syndrome.
- Trisomy 13.
- Trisomy 18.
- Cri-du-chat syndrome.
- Skeletal and neuromuscular diseases.
- Fetal alcohol syndrome.
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.
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.
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.
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 the 13th and 18th chromosomes leads to Patau syndrome and Edwards syndrome presenting micrognathia as one of their features.
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.
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.
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.
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.
Micrognathia can lead to
- Troubled eating.
- Difficulty speech.
- Breathing difficulties.
- Disrupted sleep.
- Mild facial deformity.
Last reviewed at:
11 Jan 2021 - 4 min read
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