Spondylothoracic dysostosis (STD) is a condition that affects the bones in the spine and ribs.
People with STD have bones that don’t form correctly, causing the ribs to fuse with the vertebrae, creating a fan-like shape. This fusion leads to a shorter neck and torso, resulting in a small chest. These upper-body changes can make breathing difficult and even life-threatening because the chest can’t expand properly. While the arms and legs are a regular size, the shortened torso makes affected individuals have short stature. Many people with STD may also develop hernias due to extra pressure on the diaphragm during breathing.
STD is caused by mutations in the MESP2 gene, and it can also lead to another related but less known condition called spondylocostal dystosis type 2 (SCDO2). SCDO2 is believed to be milder than STD, but it is rarer, and its exact characteristics are not well understood. Unfortunately, there is no cure for STD, so treatment focuses on managing symptoms as they appear. Infants with STD often need assistance with breathing, and hernias are fixed as needed. Healthcare providers closely monitor respiratory and cardiac (heart) function, as well as the individual’s growth and development.
As noted above, these conditions are caused by pathogenic (disease-causing) variants in the MESP2 gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background.
Another name for this condition is Jarcho-Levin syndrome.