Which are the causes of Pectus excavatum?

TL;DR: Pectus excavatum is a structural chest wall deformity characterized by the inward depression of the sternum, primarily caused by the overgrowth of the costal cartilages that connect the ribs to the breastbone. While the exact underlying cause remains under investigation, it is widely considered a developmental disorder influenced by a combination of genetic predisposition and connective tissue growth dynamics.

What causes Pectus excavatum to develop?

The primary mechanism behind Pectus excavatum is the abnormal, rapid growth of the costal cartilages. Think of the rib cage like a bridge: if the supports (the cartilages) grow longer than the space they are meant to span, the structure must buckle to accommodate the excess material. In Pectus excavatum, this buckling occurs inward toward the heart and lungs, creating the characteristic "sunken chest" appearance. While the condition is often present at birth, it frequently becomes significantly more pronounced during the adolescent growth spurt, suggesting that hormonal signals triggering rapid bone and cartilage growth play a major role in its development.

Is Pectus excavatum a genetic condition?

Research indicates that Pectus excavatum has a strong genetic component, though it does not follow a simple inheritance pattern like some other Mendelian disorders. Approximately 35% to 45% of individuals with Pectus excavatum report having a family member with the same condition, suggesting a polygenic inheritance—meaning multiple genes likely contribute to the risk. While no single "pectus gene" has been identified, the condition is frequently associated with connective tissue disorders, which are caused by mutations in genes responsible for structural proteins like collagen and fibrillin.

Are there specific risk factors or associated conditions?

While the exact cause is still being researched, several factors are known to increase the likelihood of developing Pectus excavatum. It is essential to distinguish between a "cause" (the biological driver) and a "risk factor" (an associated state). The following conditions are frequently observed alongside Pectus excavatum:

• Connective Tissue Disorders: Conditions such as Marfan syndrome, Ehlers-Danlos syndrome, and Loeys-Dietz syndrome frequently feature chest wall deformities.


• Genetic Syndromes: Individuals with Noonan syndrome or Turner syndrome have a higher statistical prevalence of this deformity.


• Growth Patterns: Rapid skeletal growth during puberty is a significant risk factor for the worsening of the depression.


• Gender: Pectus excavatum is roughly three to four times more common in males than in females, implying that sex hormones may influence cartilage development.

What does current research reveal about the etiology?

Scientists are currently focusing on the extracellular matrix—the "scaffolding" that holds cells together—to better understand why the cartilage overgrows in Pectus excavatum. Current research is exploring whether imbalances in growth factors (such as Transforming Growth Factor-beta) or localized metabolic issues within the chondrocytes (cartilage cells) lead to the asymmetrical growth patterns seen in patients. At DiseaseMaps.org, our community of 81 members provides vital anecdotal data that researchers use to better understand the range of severity and the impact of these developmental variations on daily life.

Next steps

• Consult a pediatric surgeon or a thoracic surgeon specializing in chest wall deformities for a clinical evaluation.


• Request a referral to a clinical geneticist if you have a family history of connective tissue disorders.


• Join the Pectus excavatum community at DiseaseMaps.org to connect with others sharing their experiences and management strategies.


• Keep a record of any symptoms, such as shortness of breath or exercise intolerance, to discuss during your next clinical appointment.

Medical disclaimer: This content is for informational purposes only and does not constitute professional medical advice, diagnosis, or treatment; always seek the guidance of a qualified healthcare provider with any questions regarding a medical condition.

References

• National Institutes of Health (NIH) Genetic and Rare Diseases (GARD) Information Center - Pectus excavatum profile.


• Orphanet: The portal for rare diseases and orphan drugs.


• Online Mendelian Inheritance in Man (OMIM): Database of human genes and genetic disorders.


• PubMed Central: Research articles on the pathophysiology of chest wall deformities and connective tissue interactions.