achondrogenesis /ākon′drōjen″əsis/ , the most severe form of chondrodysplasia; typically lethal before or soon after birth. Type 1A, called the Houston-Harris type, is characterized by infants with extremely short limbs, a narrow chest, short ribs that fracture easily, and soft skull bones. These infants also lack normal bone formation (ossification) in the spine and pelvis. In Type 1B, Parenti-Fraccaro type, affected infants have extremely short limbs, a narrow chest, and a prominent, rounded abdomen. The fingers and toes are short, and the feet may be rotated inward. Affected infants frequently have a soft outpouching around the umbilicus. Infants with Type 2, Langer-Saldino type, have short arms and legs, a narrow chest with short ribs, and underdeveloped lungs. This condition is also associated with a lack of ossification in the spine and pelvis. Distinctive facial features include a prominent forehead, a small chin, and in some cases an opening in the roof of the mouth (a cleft palate).
