Last reviewed by Dr. Raj MD on January 12th, 2022.
What is Micrognathia?
Micrognathia is a condition characterized by a very small lower jaw or a lower jaw that is smaller than the rest of the face. The very small size of the mandible is secondary to the abnormalities in the first branchial arch that resulted to the insufficiency or deficiency in the movement of the neural crest cells that generally occur by 4th week of fetal development or gestation.
Micrognathia commonly occurs in children and usually resolves by the time the child reaches the age of puberty when the mandible grows as the child advances in age. Micrognathia is sometime the only problem found in children born with it although it usually causes a misalignment of the teeth. Severe cases of micrognathia however may lead to a problem with feeding. The smaller size of the lower may result to a difficulty in feeding infant and children while intubation in children and adults with micrognathia may also be difficult particularly when introducing anesthesia or during an emergency situation.
The mandible or the lower jaw is regarded as the largest and the strongest bone in the face. The function of the mandible is to support or as an attachment for the lower teeth. It is composed of a body or base, rami, alveolar process, condyle and the coronoid process.
The prognosis or outlook for micrognathia depends on the underlying cause. Micrognathia generally resolves as the child advances in age or by the time the child reaches the age of puberty. The abnormality in the mandible however can be corrected with surgery especially in severe case of micrognathia.
Micrognathia is characterized by an anomaly in the anatomical structure of the lower mandible where the size is abnormally smaller than the rest of the face. The condition is first noticed during infancy and it is usually the mother who gets to notice it first.
A child with micrognathia is usually difficult to feed as the jaw would only have a small opening that a standard size of the nipple will not fit or pass through the mouth of the child. In newborn infants with micrognathia, a special nipple is required to be able to feed the baby.
Breathing is another problem that is presented in child with micrognathia. Breathing problems such as dyspnea, apnea and an abnormal rapid breathing can be observed and is due to the effect of the anomaly in the anatomical structure of the lower jaw. The abnormally small size of the lower jaw can result to an obstruction in the airway pattern as the tongue in micrognathia is in retroposition. The tongue is also prevented from growing into an average size as the lower jaw is small enough to allow it. The retroposition and the abnormal size of the tongue both make up the difficulty in breathing as both causes an obstruction in the airway.
Abnormal teeth alignment is also a presenting symptom of micrognathia. The anomaly in the size of the lower jaw provides not enough space for the teeth to grow properly or there is no enough room for a set of teeth to grow.
Causes of Micrognathia
The incidence of micrognathia is believed to be a part of an inherited disorder or is caused by a genetic mutation.
The common causes of Micrognathia include the following:
- Pierre Robin syndrome is a congenital disorder characterized by a facial malformation. Micrognathia is among the main feature of this disorder and the syndrome is by genetic anomalies particularly of chromosomes 2 and 11.
- Wolf-Hirschhorn syndrome is characterized by distinct facial abnormalities where micrognathia is included. It is a syndrome caused by depletion in the short arm of chromosome 4.
- Cri-du-Chat syndrome is a rare genetic condition caused by a deletion in chromosome 5. This syndrome is characterized by cat-like cries, developmental disabilities and physical deformities which includes an abnormally small size of the lower jaw.
- Trisomy 13 and Trisomy 18 are both genetic disorders characterized by the presence of extra genetic material. The extra genetic material resulted in a child having a severe mental deficiencies and physical deformities which include micrognathia.
- Progeria is a rare genetic condition that is not usually passed down from parents to their offspring or passed on through families. It is a condition described with a rapid aging of a child and is the consequence of a genetic mutation. Micrognathia is among the clinical feature of this condition.
Other causes of Micrognathia include the following:
- Treacher Collins syndrome
- Turner syndrome
- Russell-Silver syndrome
- Hallermann-Streiff syndrome
- Fetal alcohol syndrome
- Digeorge syndrome
- Prader-Willi syndrome
- Marfan syndrome
- Noonan syndrome
- Smith-Lemli-Opitz syndrome
- Seckel syndrome
- Juvenile idiopathic arthritis
- Goldenhar syndrome
Micrognathia is a condition that is usually present at birth. It is first noticed during infancy where the child usually has a difficulty in feeding. Micrognathia on the other hand is a condition that corrects itself by the time the child reaches the age of puberty as the mandible basically increases in size or develops while the child is advancing in age.
Treatment of micrognathia is generally not required except for the underlying cause which may need regular monitoring and treatment. Several adjustments, on the other hand are necessary to help the child thrive, such as using special equipments to feed the child and modifying the eating methods to help feed the child.
Corrective surgical procedures can be done by an orthodontist to correct the lower jaw and to align the teeth. Devices such as braces can also help in correcting the misaligned teeth that resulted from the abnormally small size of the jaw.