Achondrogenesis type 1B

Achondrogenesis type 1B is a severe form of skeletal dysplasia characterized by extremely short limbs, a narrow chest, and a prominent, rounded abdomen. This condition is caused by mutations in the SLC26A2 gene and is inherited in an autosomal recessive manner.

Clinical Features

Achondrogenesis type 1B is characterized by a lack of bone formation (ossification) in the spine and pelvis. The long bones of the arms and legs are unusually short and curved, and the ribs are also short and may be fractured. Infants with this condition have a small chest with short ribs that can restrict the growth and expansion of the lungs. They are usually stillborn or die shortly after birth from respiratory failure. Some infants have an opening in the roof of the mouth (cleft palate) and distinctive facial features including a prominent forehead, a small chin, and, in some cases, an opening in the lip (cleft lip) with or without an opening in the roof of the mouth (cleft palate).

Genetics

Achondrogenesis type 1B is caused by mutations in the SLC26A2 gene. This gene provides instructions for making a protein that is essential for the normal development of cartilage and for its conversion to bone. Mutations in the SLC26A2 gene disrupt the structure of developing cartilage, preventing bones from forming properly and resulting in the skeletal problems characteristic of achondrogenesis type 1B.

Diagnosis

The diagnosis of achondrogenesis type 1B is usually made based on clinical and radiographic criteria. Prenatal ultrasound examination may reveal characteristic findings such as short limbs, a narrow thorax, and a prominent abdomen. After birth, radiographic studies typically show a lack of ossification in the spine and pelvis, short and curved long bones, and short ribs. Genetic testing can confirm the diagnosis.

Treatment

There is currently no cure for achondrogenesis type 1B. Treatment is supportive and based on the signs and symptoms present in each person. Because of the severe health problems associated with achondrogenesis type 1B, affected infants usually do not survive past the neonatal period.

See Also

• Skeletal dysplasia
• SLC26A2
• Autosomal recessive
• Cleft palate
• Cleft lip

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