Achondrogenesis

Written by Chitra Badii | Published on July 25, 2012
Medically Reviewed by George Krucik, MD

Overview

Achondrogenesis is a rare and severe group of genetic disorders that results in a short trunk, small limbs, and a narrow chest. It occurs when a person’s body does not produce enough growth hormone. As a result, cartilage and bone do not develop properly, causing abnormalities in the skeletal system.

You are more likely to have a child with this disorder if both you and your partner carry the gene. Most babies with achondrogenesis die before or right after birth because they cannot breathe properly. No treatments exist for the disorder. Care focuses on making the baby as comfortable as possible for the duration of his or her life.

Types of Achondrogenesis

This disorder is usually categorized into three different types based on the pattern of inheritance, signs, and symptoms.

Type 1A

In achondrogenesis type 1A, the baby’s skull bone is very soft and the limbs are very short. As with all three types, the chest is narrow, making it hard for the baby to breathe. The bones in the spine and pelvis do not form well. The baby also has short ribs that break easily.

Type 1B

Type 1B is very similar to 1A, and distinguishing between the two types often requires a genetic test. In addition to the very short limbs and narrow chest, type 1B includes a round belly and sometimes a pouch near the groin or belly button. If your baby has this type of achondrogenesis, his or her feet may be inwardly rotated. The toes and fingers are also very short.

Type 2

As with the other two types, babies born with type 2 achondrogenesis have short limbs and a narrow chest. Their ribs are usually short and their lungs are not well developed. The bones in the spine and pelvis are not well formed. The roof of the mouth may have an opening (cleft palate). A small chin and large forehead are other signs. The belly may be large, and some infants will have too much fluid in their bodies before they are born.

Statistics have been collected for the occurrence of type 2 achondrogenesis and a similar bone growth disorder called hypochondrogenesis. Together, the conditions have been observed in one in every 40,000 to 60,000 infants.

What Causes Achondrogenesis?

This rare disorder runs in families. If both you and your partner carry the gene, there is a 25 percent chance that your child will have the condition. Since the genetic disorder is recessive the parental carriers of the gene, show no signs of the condition.

What Are the Symptoms of Achondrogenesis?

Short limbs and a narrow chest are common to all types of achondrogenesis. The other symptoms vary by type. Genetic testing may be necessary to distinguish the exact type.

Type 1A Symptoms

  • soft skull bone
  • poorly formed spine and pelvic bones
  • short and easily breakable ribs

Type 1B Symptoms

  • round belly
  • pouch near the belly button
  • short toes and fingers
  • inwardly rotated feet

Type 2 Symptoms

  • short ribs
  • poorly developed lungs
  • cleft palate
  • small chin
  • large forehead and belly

How Is Achondrogenesis Diagnosed?

Your doctor will order X-rays to examine the baby’s bones. Usually, the signs are obvious to the human eye, and the doctor will know right away if the baby has some type of the condition.

Treating Achondrogenesis

No treatments exist for achondrogenesis. To keep the baby as comfortable as possible, the hospital will monitor him or her and possibly use a breathing machine. Medication may also be needed to limit pain and discomfort.

What Can Be Expected in the Long Run?

Babies born with achondrogenesis usually die quickly because their small chests do not allow them to breathe. Many die in utero.

Preventing Achondrogenesis: Genetic Counseling

If achondrogenesis exists in your family, your only option for preventing the disorder is to have genetic counseling prior to starting a family. During genetic counseling, a specialist will collect your medical histories, asking about illnesses that have occurred on both sides of your families. Medical practitioners will run tests to determine whether you and your partner are carrying the genes for achondrogenesis. Couples with a family history of achondrogenesis might choose to exercise this option before deciding whether or not to have a baby.

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