Hypochondrogenesis is a severe, inherited disorder of bone growth. This condition is characterized by a short body and limbs and abnormal bone formation in the spine and pelvis. Hypochondrogenesis is a subtype of collagenopathy, types II and XI. This condition is similar to another skeletal disorder, achondrogenesis, type 2; however, the spinal changes seen in hypochondrogenesis tend to be somewhat milder. Affected infants have short arms and legs, a small chest with short ribs, and underdeveloped lungs. The spinal bones (vertebrae) in the neck and part of the pelvis (the sacrum) do not harden, or ossify, properly. The face appears flat and oval-shaped, with widely spaced eyes, a small chin, and, in some cases, an opening in the roof of the mouth called a cleft palate. The abdomen is enlarged, and excess fluid may build up in the body before birth (a condition called hydrops fetalis). As a result of these serious health problems, infants are usually premature and stillborn or die shortly after birth from respiratory failure. Some infants have lived for a time, however, with intensive medical support. Babies who live past the newborn period are usually reclassified as having spondyloepiphyseal dysplasia congenita, a related disorder on the spectrum of abnormal bone growth.