What is achondrogenesis?
Achondrogenesis is a group of genetic disorders that severely affect cartilage and bone development in unborn babies. The condition is a type of osteochondrodysplasia, which causes several types of short stature (dwarfism) due to abnormal bone and cartilage growth.
Achondrogenesis has three main types (1A, 1B and 2), and each has slightly different signs, symptoms and causes. With all types, babies have a higher chance of being born prematurely or being stillborn. Achondrogenesis causes severely underdeveloped lungs, and because of this, babies who have the condition don’t survive more than a few days after birth.
What causes achondrogenesis?
Genetic mutations (changes in genes) cause achondrogenesis; each type of achondrogenesis is related to a specific mutation. Mutations that a person inherits from both parents cause achondrogenesis types 1A and 1B. Type 2 almost always results from new mutations that happen at conception in babies who have no family history of the disorder.
Who gets achondrogenesis?
Achondrogenesis affects males and females equally. Achondrogenesis type 1A and type 1B are very rare disorders, and researchers aren’t sure how frequently they occur. Achondrogenesis type 2 occurs in about one out of 40,000 to 60,000 births.
What are the signs and symptoms of achondrogenesis?
Doctors can detect some signs and symptoms of achondrogenesis on a prenatal ultrasound. Signs that occur with all types include:
- Extremely short arms and legs
- Poor spine bone formation
- Unusually large head
- Short torso
- Very narrow chest with a bulging belly
- Excess amniotic fluid (the fluid that surrounds and protects your baby in your uterus), known as polyhydramnios
- Fluid buildup in the fetus’s skin or scalp, or around the heart or lungs (hydrops fetalis)
Each type of achondrogenesis also has some unique signs. The main types are:
- Type 1A: Also called the Houston-Harris type, this form is the most severe. Signs of achondrogenesis type 1A include:
- Poor skull bone formation
- Short ribs that fracture easily
- Type 1B: Signs and symptoms of achondrogenesis type 1B (Parenti-Fraccaro type) include:
- Poor skull bone formation
- Hernia (tissue that bulges through an abnormal opening) near the belly button or groin
- Type 2: Sometimes called the Langer-Saldino type, achondrogenesis type 2 causes unusual facial features, including:
- Prominent forehead
- Small chin
- Cleft palate (opening in the roof of the mouth)
What tests are used to diagnose achondrogenesis?
Your doctor may see signs of achondrogenesis during your pregnancy with a routine ultrasound. You’ll then have additional tests during pregnancy to confirm a diagnosis. Tests may include:
- Amniocentesis: Your doctor uses a thin needle inserted through your belly into your uterus to take a small sample of amniotic fluid. This test detects chromosomal and genetic disorders such as achondrogenesis.
- Chorionic villus sampling (CVS): Your doctor takes a small sample of tissue from the placenta (organ inside your uterus that nourishes your baby). We may take the sample with a needle inserted through your belly or a thin tube through your vagina and cervix. CVS is another test that can detect genetic and chromosomal disorders. Find out more about amniocentesis, CVS and our other prenatal genetic testing.
- Fetal ultrasound: We examine your baby with a targeted, detailed ultrasound to look for bone and cartilage problems that can be signs of achondrogenesis.
If the condition goes undetected during pregnancy, our fetal care specialists can diagnose achondrogenesis after a baby is born with:
- A physical exam to confirm signs of the condition
- X-rays to evaluate bones and cartilage in the skull, spine and other areas
- Genetic testing
How is achondrogenesis treated?
Unfortunately, no treatment can cure or manage achondrogenesis. Babies with achondrogenesis pass away either during pregnancy (miscarriage or stillbirth) or within a few days of birth. At Children’s Hospital Colorado, we’ll discuss all your care options with you and answer any questions you have.
Why choose us for achondrogenesis treatment?
Learning that your baby may have achondrogenesis is upsetting and may be frightening. At the Colorado Fetal Care Center, we understand the pain of this diagnosis and have the support services to help your family. We provide compassionate care to guide you through a difficult time.
Babies with achondrogenesis can typically be born vaginally, unless your team recommends a cesarean delivery for other health reasons. Even though babies with achondrogenesis pass away within the first days of life, we still provide comfort care for you and your baby to relieve pain and other symptoms through our Neonatal Palliative Care Program. We also offer prenatal counseling and ongoing mental health support for parents and families.
- National Institutes of Health, Genetic and Rare Diseases Information Center: Achondrogenesis
- National Institutes of Health, U.S. National Library of Medicine: Achondrogenesis
- Denver Share, grief support for bereaved parents: Denver Share
Could I have another child with achondrogenesis?
It depends on the type of achondrogenesis that your child has. With types 1A and 1B, each of your children has a 25% chance of developing the disorder. Type 2 usually does not occur in other children in the same family.
Do I have to undergo amniocentesis or chorionic villus sampling before delivery?
No, you may not need to have an amniocentesis or CVS during pregnancy. Some families wait until after birth to do genetic testing. However, the information gained through genetic testing can help your doctor plan your and your baby's care during pregnancy, delivery and afterward.
Did I do anything to cause achondrogenesis in my baby?
Nothing that a parent does can cause achondrogenesis. You cannot control which genes you pass on to your children, for the inherited types. And you cannot control whether new gene mutations happen when the sperm cell and egg cell combine at conception.