Achondrogenesis refers to a group of conditions that cause severe problems with the development of bone and cartilage in the womb.
Babies with achondrogenesis usually die before or shortly after birth. With the right medical support, some babies live for a brief period.
In this article, we look at what achondrogenesis is, what causes it, how doctors detect it, and how parents and caregivers can receive support.
Achondrogenesis refers to a group of fatal genetic disorders that affect the development of bone and cartilage.
Babies with any of these disorders may have short limbs, small bodies, and cleft palate, as well as developmental differences.
Most babies with achondrogenesis die before or shortly after birth because they are unable to breathe.
There are three distinct types, and characteristics and inheritance patterns differ.
Type 1A
Type 1A, sometimes called the Houston-Harris type, causes a baby to have:
- short limbs
- bones that easily fracture
- abnormal bone development in the spine, skull, and pelvis
- facial abnormalities
A baby born with this type may have a small, underdeveloped chest, leading to life threatening breathing difficulties.
Type 1B
Type 1B, also known as the Fraccaro type, causes a baby to have:
- a short trunk and limbs
- short fingers
- unusually shaped toes
- a large stomach
Type 2
Type 2, or Langer-Saldino type, causes a baby to have:
- a narrow chest
- small bones in the legs or arms
- underdeveloped lungs
- abnormal bone growth in the pelvis and spine
Some babies with this type also have swelling because fluid has built up in their stomachs.
Achondrogenesis is a genetic disorder, which means that babies develop it because of abnormalities in their genes. A parent can do nothing to cause or prevent the condition.
Types 1A and 1B are autosomal recessive disorders — they develop when both parents carry an abnormal copy of a specific gene. A mutation in the TRIP11 gene causes type 1A achondrogenesis, while a mutation in the SLC26A2 gene causes type 1B.
Parents who are closely related are more likely to have a child with achondrogenesis because it is more likely that close relatives carry the same genetic mutations.
When both parents carry a genetic mutation linked with achondrogenesis, their child has a:
- 25% chance of having the disorder
- 25% chance of neither having the disorder nor carrying the mutation
- 50% chance of not having achondrogenesis but carrying the genetic mutation
Testing during pregnancy may help identify achondrogenesis. Also, genetic counseling can help parents weigh the risks and benefits of subsequent pregnancies.
Most cases of type 2 achondrogenesis involve a de novo mutation — a new mutation in a family line, not something that a parent has passed down.
Changes in the COL2A1 gene cause type 2, but researchers do not understand what causes these mutations or whether anything can prevent them.
A doctor can usually diagnose achondrogenesis by looking at an ultrasound during weeks 12–14 of pregnancy. Because achondrogenesis may resemble other conditions, the doctor may recommend additional testing, such as amniocentesis.
Genetic testing may be available for people with a higher chance of passing on achondrogenesis, such as those with a family history of the disorder.
People with a family history should consult a genetic counselor early in pregnancy or before trying to become pregnant.
Achondrogenesis is very rare. Types 1A and 1B are so rare that researchers do not know the prevalence. Type 2 occurs in around 1 in 40,000 to 1 in 60,000 newborns.
The disorder is equally common in males and females.
When both parents carry an associated genetic mutation, the chance that their child will have achondrogenesis type 1A or 1B is 1 in 4, experts estimate.
When some members of a family have had a child with achondrogenesis, other people in the family have an increased likelihood of also carrying the associated mutation.
Some parents choose to terminate the pregnancy, while others choose to continue with it.
No treatment can cure achondrogenesis. In most cases, the baby dies before or shortly after birth. Sometimes the baby is stillborn.
Healthcare professionals focus on minimizing pain for the woman and baby and providing support to both parents.
Parents of babies with achondrogenesis should receive genetic counseling to assess the likelihood of having another child with this condition.
Babies with achondrogenesis cannot survive for long outside of the womb. Whether the parents choose to terminate or continue with the pregnancy, the experience can be very emotionally painful.
Parents who decide to terminate may fear judgment and stigma and may be uncomfortable talking about the experience.
Several organizations work to help parents who have experienced the loss of a baby before or shortly after birth. Among them are:
- Share — Pregnancy and Infant Loss Support
- Mommies Enduring Neonatal Death
- Exhale, which provides support after abortion
The Compassionate Friends organization also provides support for families after the death of a child.
When an infant dies or termination occurs later in pregnancy, a woman may have a higher risk of postpartum depression. Receiving medical and psychological care is critical to her well-being.
Appropriate postpartum care can prevent long-term health issues and help parents cope with challenges. For example, if breast milk comes in after the loss of a baby, one or both parents may find this difficult, emotionally and otherwise.
Family and friends can offer support by:
- talking about the baby as a person and using the baby’s name
- not comparing the death of the baby to an early pregnancy loss, or miscarriage
- acknowledging the choices of the parents as valid and reasonable
- neither judging or shaming the parents if they decided to terminate the pregnancy
- offering material support, such as meals or care for other children
- helping the parents find ways to memorialize the baby
- attending the funeral, if the parents choose to have one
While achondrogenesis is an incurable, fatal disease, many organizations are researching options that might one day offer more hope.
At present, genetic testing can reveal the likelihood of passing a mutation linked with achondrogenesis on to a child.
Undergoing genetic testing can help guide reproductive decisions. Testing very early in pregnancy and consulting healthcare professionals can help people make more informed choices.