Although current medicine has developed to the molecular and genetic levels, the true causes of many modern diseases are still not completely clear, which includes pectus excavatum. There have been medical cases indicating that scientists have never ceased to explore the causes of pectus excavatum. It was once believed by early medical scientists that pectus excavatum might be caused by the inward and backward pulling of the sternum by the diaphragm. Therefore, for a period, the treatment for pectus excavatum involved releasing adhesions of the diaphragm, but this method was later found to be ineffective for children and was abandoned. Subsequently, it was discovered that pectus excavatum is somewhat related to the genetics of many families, such as those with Marfan syndrome (an autosomal dominant hereditary connective tissue disorder) and Noonan syndrome (a genetic disorder caused by mutations). However, no definitive pathogenic genes have been identified in families with sporadic cases of pectus excavatum. In summary, pectus excavatum is currently believed to be possibly caused by factors such as the development of rib cartilage on both sides, genetics, and other acquired conditions, like underdeveloped laryngeal cartilage or post-surgical factors from congenital diaphragmatic hernia repair. Overall, the causes of pectus excavatum are still actively being explored by medical scientists.