Achondrogenesis type 2

Achondrogenesis type 2 (ACG2) is a rare, lethal genetic disorder affecting the development of the skeletal system. It is one of the types of achondrogenesis, a group of severe disorders that are present from birth and affect the development of cartilage and bone.

Etiology

ACG2 is caused by mutations in the COL2A1 gene. This gene provides instructions for making a protein that forms type II collagen, a molecule found mostly in cartilage and in the clear gel that fills the eyeball (vitreous). The mutations interfere with the assembly of type II collagen molecules, which prevents bones and other connective tissues from developing properly.

Clinical Features

Infants with ACG2 have short arms and legs, a small chest with short ribs, and underdeveloped lungs. They also have an enlarged abdomen, and a soft skull and bones. Other features include a prominent forehead, a small chin, and, in some cases, an opening in the roof of the mouth (cleft palate). Due to the severity of the symptoms, most infants with ACG2 do not survive beyond early infancy.

Diagnosis

Diagnosis of ACG2 is based on clinical and radiographic criteria. Prenatal ultrasound may show characteristic features such as short limbs, a small chest, and underdeveloped lungs. After birth, X-ray studies can reveal characteristic changes in the bones and cartilage. Genetic testing can confirm the diagnosis by identifying a mutation in the COL2A1 gene.

Treatment

There is currently no cure for ACG2. Treatment is supportive and focuses on managing the symptoms. This may include respiratory support for underdeveloped lungs and surgery to repair a cleft palate.

Epidemiology

ACG2 is extremely rare, with an estimated prevalence of less than 1 in 1,000,000. It affects both males and females equally.

See Also

• Achondrogenesis
• COL2A1
• Genetic disorder
• Skeletal system

NIH genetic and rare disease info

• NIH info on Achondrogenesis type 2

Achondrogenesis type 2 is a rare disease.