Spondylocostal dysostosis is a rare syndrome characterized by short-trunk dwarfism secondary to developmental anomalies of the vertebrae and ribs. Previously the condition spondylothoracic dysostosis was grouped together with spondylocostal dysostosis, often under the term Jarcho-Levin syndrome, but the two diseases are now considered to be distinct entities.
A rare condition, almost 400 cases of spondylocostal dysostosis have been described in the literature 1.
Spondylocostal dysostosis is characterized by a short-trunk dwarfism phenotype (normal length upper and lower limbs with a disproportionately-reduced size central body) due to the maldevelopment of the vertebrae and ribs. A mild kyphoscoliosis is often present.
The abnormal development of the ribs results in absent and/or fused ribs, such that overall the thoracic cavity is reduced in total volume leading to breathing difficulties, which can be life-threatening. Due to a lack of room in which to inflate, the lungs expand inferiorly, pushing down on the abdominal viscera with secondary herniae which may include umbilical, diaphragmatic, and inguinal types.
Associated abnormalities include cardiac and genitourinary anomalies, and occasionally neural tube defects.
Mutations have been found in several genes (DLL3, MESP2, LNFG, and HES7) coding for proteins from the Notch signaling pathway. This pathway is important in the process of somite segmentation, central to the development of the vertebrae and ribs.
History and Etymology
Saul Jarcho and Paul Levin first described the condition at Johns Hopkins in 1938 4.