What causes pectus carinatum?

Causes of Pectus Carinatum

Pectus carinatum is primarily caused by abnormal overgrowth of costal cartilages, and is frequently associated with connective tissue disorders like Marfan syndrome, which results from mutations in the FBN1 gene that encodes fibrillin-1, a key component of microfibrils in the extracellular matrix. 1, 2

Genetic and Developmental Factors

• Connective Tissue Disorders: Pectus carinatum is strongly associated with heritable connective tissue disorders:

  • Marfan syndrome (FBN1 gene mutations) 1, 2
  • Loeys-Dietz syndrome (TGFBR1, TGFBR2, SMAD3, TGFB2, TGFB3 mutations) 1
  • Noonan syndrome 2, 3

• Pathophysiology: The underlying mechanism involves:

  • Abnormal overgrowth of costal cartilages connecting the ribs to the sternum 4
  • Defects in fibrillin-1 and related extracellular matrix proteins that provide structural support 1
  • Dysregulation of TGF-β signaling pathways affecting connective tissue development 1

Clinical Associations and Presentations

• Skeletal Manifestations: Pectus carinatum often presents alongside other skeletal abnormalities:

  • Straight thoracic spine 2
  • Scoliosis 1
  • Dolichostenomelia (long limbs) 1
  • Arachnodactyly (long, slender fingers) 1
  • Joint hypermobility 1

• Scoring System: In Marfan syndrome diagnosis, pectus carinatum is considered a significant systemic feature:

  • Pectus carinatum deformity scores 2 points in the systemic features scoring system 1
  • Pectus excavatum or chest asymmetry scores 1 point 1

Differential Considerations

• Isolated vs. Syndromic: Pectus carinatum may present as:

  • An isolated deformity without other systemic features 5
  • Part of a broader connective tissue disorder syndrome 1, 2
  • Familial pectus deformity without identified genetic mutation 1

• Types of Pectus Carinatum:

  • Standard form with outward protrusion of the sternum 5
  • Pectus arcuatum variant with abnormally short, fully fused sternum and high anterior protrusion 5

Clinical Implications

• Psychological Impact: Unlike pectus excavatum, pectus carinatum rarely causes physiological impairment but can have significant psychological effects:

  • Disturbed body image 6
  • Lower self-esteem 6
  • Reduced quality of life 6

• Evaluation: When pectus carinatum is identified, evaluation should include:

  • Screening for features of Marfan syndrome and related disorders 2
  • Echocardiography to assess for aortic root dilation and valve abnormalities if syndromic features are present 2
  • Evaluation of the spine for scoliosis 2

Management Considerations

• Treatment Priority: In patients with both pectus carinatum and aortic root dilation:

  • Cardiovascular management takes precedence over pectus repair 2
  • Aortic root surgery should be performed before pectus correction if the aortic root is ≥4.5 cm 2

• Treatment Options:

  • Dynamic compression bracing for flexible chest walls in compliant patients 5
  • Surgical correction (modified Ravitch technique) for severe or rigid deformities 4, 3
  • Psychological support and counseling 6

The presence of pectus carinatum should prompt consideration of underlying connective tissue disorders, particularly when accompanied by other skeletal, ocular, or cardiovascular manifestations.