Achondrogenesis
Achondrogenesis is a group of severe disorders that are present from birth and affect the development of cartilage and bone. Infants with achondrogenesis usually have a small body, extremely short arms and legs, other skeletal abnormalities, and underdeveloped lungs. There are at least three forms of achondrogenesis, type 1A, type 1B and type 2. Achondrogenesis is usually diagnosed during pregnancy by ultrasound and genetic testing is used to distinguish between the three types. Type 1A and 1B achondrogenesis are both inherited in an autosomal recessive pattern. Type 1A is caused by mutations in the TRIP11 gene. Type 1B is caused by mutations in the SLC26A2 gene. Type 2 achondrogenesis is caused by new (de novo) mutations in the COL2A1 gene. Because of the severity of this condition, most infants with achondrogenesis die before or shortly after birth.