What is micrognathia?

Micrognathia is a condition in which the lower jaw is undersized. It is a symptom of a variety of craniofacial conditions. Sometimes called mandibular hypoplasia, micrognathia may interfere with your baby’s feeding and breathing.

If micrognathia is found during your pregnancy, you will be referred to a fetal medicine specialist who will perform detail ultrasound scan to assess your baby and look for associated issues, or underlying causes. They may offer you further tests (see investigations section). You will be scanned regularly to assess for polyhydramnios (extra fluid build up around the baby due to gastrointestinal obstruction by the tongue).

If micrognathia is thought to be significant, there can be difficulties with airway management at birth. In these cases you would be referred to St Michael’s fetal medicine unit in Bristol to plan delivery with appropriate expertise from ear, nose and throat surgeons as well specialist neonatologists who are skilled in managing for difficult airways in babies.

Micrognathia is fairly common in infants, and can often corrects itself as your baby grows. In some children, micrognathia can cause abnormal tooth alignment because there is not enough room in your child’s mouth for the teeth to grow.

Micrognathia can occur as a feature of numerous syndromes, including  cleft lip/palate, Pierre Robin sequence, Treacher Collins syndrome, Beckwith Wiedemann syndrome, Stickler’s syndrome and others.

Potential genetic causes

• Around 30% of micrognathia cases will have an underlying chromosomal anomaly, particularly Trisomy 18 and triploidy.
• Micrognathia can be associated with many genetic syndromes, including:
  • Pierre Robin sequence, which is associated with micrognathia, cleft palate and backward positioned tongue, and may be associated with an underlying genetic diagnosis and/or other structural anomalies;
  • Treacher Collins syndrome, which is associated with underdevelopment of the jaw bones called the maxilla and zygoma, micrognathia, cleft palate and malformed or absent ears. This happens due to variations in certain genes of the POLR family.

More information can be found here.