Achondrogenesis type 2
Encyclopedia
Infants with achondrogenesis, type 2 have short arms and legs, a small chest with short ribs, and underdeveloped lungs. Achondrogenesis, type 2 is a subtype of collagenopathy, types II and XI
. This condition is also associated with a lack of bone formation (ossification) in the spine and pelvis. Typical facial features include a prominent forehead, a small chin, and, in some cases, an opening in the roof of the mouth (a cleft palate). The abdomen is enlarged, and affected infants often have a condition called hydrops fetalis in which excess fluid builds up in the body before birth. The skull
bones may be soft, but they often appear normal on X-ray
images. In contrast, bones in the spine (vertebrae) and pelvis do not harden.
Achondrogenesis, type 2 and hypochondrogenesis
(a similar skeletal disorder) together affect 1 in 40,000 to 60,000 births. Achondrogenesis, type 2 is one of several skeletal disorders caused by mutations in the COL2A1 gene. This gene provides instructions for making a protein that forms type II collagen
. This type of collagen is found mostly in cartilage and in the clear gel that fills the eyeball (the vitreous). It is essential for the normal development of bones and other tissues that form the body's supportive framework (connective tissues). Mutations in the COL2A1 gene interfere with the assembly of type II collagen molecules, which prevents bones and other connective tissues from developing properly.
Achondrogenesis, type 2 is considered an autosomal dominant disorder because one copy of the altered gene in each cell is sufficient to cause the condition. The disorder is not passed on to the next generation, however, because affected individuals hardly survive past puberty.
Collagenopathy, types II and XI
The type II and XI collagenopathies are a group of disorders that affect connective tissue, the tissue that supports the body's joints and organs. These disorders are caused by defects in type II or type XI collagen. Collagens are complex molecules that provide structure, strength, and elasticity ...
. This condition is also associated with a lack of bone formation (ossification) in the spine and pelvis. Typical facial features include a prominent forehead, a small chin, and, in some cases, an opening in the roof of the mouth (a cleft palate). The abdomen is enlarged, and affected infants often have a condition called hydrops fetalis in which excess fluid builds up in the body before birth. The skull
Human skull
The human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...
bones may be soft, but they often appear normal on X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
images. In contrast, bones in the spine (vertebrae) and pelvis do not harden.
Achondrogenesis, type 2 and hypochondrogenesis
Hypochondrogenesis
Hypochondrogenesis is a severe genetic disorder causing malformations of bone growth. The condition is characterized by a short body and limbs and abnormal bone formation in the spine and pelvis....
(a similar skeletal disorder) together affect 1 in 40,000 to 60,000 births. Achondrogenesis, type 2 is one of several skeletal disorders caused by mutations in the COL2A1 gene. This gene provides instructions for making a protein that forms type II collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
. This type of collagen is found mostly in cartilage and in the clear gel that fills the eyeball (the vitreous). It is essential for the normal development of bones and other tissues that form the body's supportive framework (connective tissues). Mutations in the COL2A1 gene interfere with the assembly of type II collagen molecules, which prevents bones and other connective tissues from developing properly.
Achondrogenesis, type 2 is considered an autosomal dominant disorder because one copy of the altered gene in each cell is sufficient to cause the condition. The disorder is not passed on to the next generation, however, because affected individuals hardly survive past puberty.