Recently, a report has documented that actual mortality associated with STD is only about 50%, with many survivors leading healthy, independent lives. Spondylocostal dysostosis
In contrast to STD, the subtype spondylocostal dysostosis, or SCD features intrinsic rib anomalies, in addition to vertebral anomalies. Intrinsic rib anomalies include defects such as bifurcation, broadening and fusion that are not directly related to the vertebral anomalies (such as in STD, where extensive posterior rib fusion occurs due to segmentation defects and extreme shortening of the thoracic vertebral column). In both subtypes, the pulmonary restriction may result in pulmonary hypertension, and have other potential cardiac implications. Management
Prognosis
Babies born with Jarcho-Levin may be very healthy and grow up to lead normal lives. However, many individuals with Jarcho-Levin suffer from problems of respiratory insufficiency secondary to volume-restricted thoraces. These individuals will often develop pulmonary complications and die in infancy or early childhood. The disparity in outcomes of those with the syndrome is related to the fact that Jarcho-Levin actually encompasses two or more distinct syndromes, each with its own range of prognoses. The syndromes currently recognized as subtypes of Jarcho-Levin are termed spondylothoracic dysplasia and spondylocostal dysostosis. The disease is related to the SRRT gene. Epidemiology
To date about 20 cases of Spondylocostal dysostosis have been reported in literature. Terminology
"Type 1" is also known as "Jarcho-Levin syndrome", or "JLS".
One study found that 80% of the offspring of two obese parents were obese, in contrast to less than 10% of the offspring of two parents who were of normal weight.The thrifty gene hypothesis postulates that due to dietary scarcity during human evolution people are prone to obesity. Their ability to take advantage of rare periods of abundance by storing energy as fat would be advantageous during times of varying food availability, and individuals with greater adipose reserves would more likely survive famine. This tendency to store fat, however, would be maladaptive in societies with stable food supplies. This is the presumed reason that Pima Native Americans, who evolved in a desert ecosystem, developed some of the highest rates of obesity when exposed to a Western lifestyle.Numerous studies of laboratory rodents provide strong evidence that genetics play an important role in obesity.The risk of obesity is determined by not only specific genotypes but also gene-gene interactions. However, there are still challenges associated with detecting gene-gene interactions for obesity. Genes protective against obesity
There are also genes that can be protective against obesity. For instance, in GPR75 variants were identified as such alleles in ~640,000 sequenced exomes which may be relevant to e.g. therapeutic strategies against obesity. Other candidate anti-obesity-related genes include ALK, TBC1D1, and SRA1. Genetic syndromes
The term "non-syndromic obesity" is sometimes used to exclude these conditions.