Spondylothoracic dysostosis

Spondylothoracic dysostosis is inherited in an autosomal recessive fashion. This means that to be affected, a person must have a mutation in both copies of the responsible gene in each cell. Affected people inherit one mutated copy of the gene from each parent, who is referred to as a carrier. Carriers of an autosomal recessive condition typically do not have any signs or symptoms (they are unaffected).^[1]

Spondylothoracic dysostosis (STD) is a rare condition that affects the bones of the spine and the ribs.^[2] The term “Jarcho-Levin syndrome” in many cases is used as a synonym for STD, and sometimes as a synonym for another condition known as spondylocostal dysostosis, which has several common features with STD. Also, the term “Jarcho-Levin syndrome” is often used for all radiologic features that include defects of the vertebrae and abnormal rib alignment.^[3] Signs and symptoms of STD are generally present at birth and may include short-trunk dwarfism (a short body with normal length arms and legs); a small chest cavity; misshapen and abnormally-fused vertebrae (bones of the spine); and fused ribs at the part nearest the spine. Affected people may also have life-threatening breathing problems and recurrent lung infections, which can significantly reduce lifespan. It can occur in any population; however, it occurs most frequently in people of Puerto Rican ancestry.^[1] It is caused by changes (mutations) in the MESP2 gene and is inherited in an autosomal recessive manner.^[2][1][4] Treatment is based on the signs and symptoms present and may include surgery for bone malformations and respiratory support.^[4]

Signs and symptoms of spondylothoracic dysostosis include spine and vertebral abnormalities, which result in a shortened spine, neck, and trunk, as well as rib anomalies including fused ribs. This combination of features result in a "crab-like" appearance to the rib cage. Although the neck and midsection of individuals with spondylothoracic dysostosis are shortened, the arms and legs grow normally. As such, individuals with spondylothoracic dysostosis have short stature and are said to have short-trunk dwarfism.^[1][2]

The spine and rib abnormalities may cause other complications. Infants with this condition are born with a small chest that cannot expand appropriately. This often leads to life-threatening breathing problems. As the lungs expand, the narrow chest forces the muscle that separates the abdomen from the chest cavity (the diaphragm) 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) or belly-button (umbilical hernia).^[2]

Most individuals with spondylothoracic dysostosis have normal intelligence and neurological problems are infrequent.^[5]

Symptom severity may vary from patient to patient with spondylothoracic dysostosis; however, symptoms tend to be the worse for individuals who carry two E230X mutations in the MESP2 gene.^[1]

There is no cure for spondylothoracic dysostosis. Treatment usually consists of intensive medical care, including early and aggressive treatment of respiratory infections, physical therapy, bone surgery, and orthopedic treatment.^[6][7] Surgery may then be needed for chest wall or spine deformities, such as severe scoliosis. An external bracing, for example, by use of an expandable prosthetic titanium rib may be used for some cases.^[3]  

To find a medical professional who specializes in genetics, you can ask your doctor for a referral or you can search for one yourself. Online directories are provided by the American College of Medical Genetics and the National Society of Genetic Counselors. If you need additional help, contact a GARD Information Specialist. You can also learn more about genetic consultations from Genetics Home Reference.