Spondylocostal dysostosis

Spondylocostal dysostosis is a group of conditions characterized by abnormal development of bones in the spine and ribs. The bones of the spine (vertebrae) are misshapen and abnormally joined together (fused). Many people with this condition have abnormal side-to-side curvature of the spine (scoliosis) due to malformation of the vertebrae. In addition to spinal abnormalities, some of the rib bones may be fused together or missing. Affected individuals have short, rigid necks and short torsos because of the bone malformations. As a result, people with spondylocostal dysostosis have short bodies but normal-length arms and legs, called short-trunk dwarfism.

The spine and rib abnormalities, which are present from birth, cause other signs and symptoms of spondylocostal dysostosis. Infants with this condition have small chests that cannot expand adequately, often leading to life-threatening breathing problems. As the lungs expand in the narrow chest, the muscle that separates the abdomen from the chest cavity (the diaphragm) is forced down and the abdomen is pushed out. The increased pressure in the abdomen can cause a soft out-pouching around the lower abdomen (inguinal hernia), particularly in males with spondylocostal dysostosis.

Some people with spondylocostal dysostosis also have a type of birth defect known as a neural tube defect. Neural tube defects occur when a structure called the neural tube, a layer of cells that ultimately develops into the brain and spinal cord, fails to close completely during the first few weeks of embryonic development. Examples of neural tube defects that occur in people with spondylocostal dysostosis include a spinal cord abnormality known as spina bifida and a brain abnormality called a Chiari malformation.

Although breathing problems can be fatal early in life, many affected individuals live into adulthood.

Spondylocostal dysostosis has often been grouped with a similar condition called spondylothoracic dysostosis, and both are sometimes called Jarcho-Levin syndrome; however, they are now considered distinct conditions.