What causes pectus carinatum?

Causes of Pectus Carinatum

Pectus carinatum is primarily caused by abnormal growth of costal cartilages, often with genetic predisposition, and is frequently associated with connective tissue disorders such as Marfan syndrome and other genetic conditions. 1

Etiopathogenesis

Pectus carinatum (PC), also known as "keel chest," represents a spectrum of progressive inborn anomalies of the anterior chest wall characterized by protrusion of the sternum and/or adjacent costal cartilages. The main theories regarding its development include:

• Cartilage Overgrowth: The leading hypothesis focuses on overgrowth or growth disturbance of costal cartilages 1
• Genetic Factors: Strong evidence supports genetic predisposition 2
• Connective Tissue Disorders: Frequently associated with various connective tissue disorders 3

Associated Conditions

Pectus carinatum is often not an isolated finding but associated with several conditions:

• Marfan syndrome - A common association found in up to 50% of patients under 40 years with aortic dissection 4
• Other connective tissue disorders:
  • Homocystinuria
  • Osteogenesis imperfecta
  • Noonan syndrome
  • Ehlers-Danlos syndrome 5, 3
• Other associated conditions:
  • Prune belly syndrome
  • Morquio syndrome
  • Mitral valve prolapse 5

Clinical Presentation and Features

Unlike pectus excavatum (which often presents with cardiopulmonary symptoms), patients with pectus carinatum primarily present with:

• Cosmetic concerns: The most common complaint 1
• Orthopedic findings: May include joint hypermobility, scoliosis, and other skeletal abnormalities 3
• Physical exam findings: Typically include visible protrusion of the sternum or adjacent costal cartilages

Diagnostic Approach

When evaluating a patient with suspected pectus carinatum:

• Physical examination: Look for associated features of connective tissue disorders as outlined in Table 1 of the guidelines, including ophthalmologic findings (ectopia lentis, myopia), skin findings (striae, translucent skin), and orthopedic findings (joint hypermobility, scoliosis) 4
• Imaging:
  • Chest radiography as initial screening
  • CT scans for precise characterization of anatomy and degree of deformity
  • Consider echocardiography to assess for associated cardiac abnormalities, especially in patients with suspected Marfan syndrome 3

Clinical Implications

Understanding the etiology is important because:

1. Associated conditions may require treatment priority: Cardiovascular management always takes precedence over pectus repair in patients with Marfan syndrome 3
2. Genetic testing: Should be considered when associated with syndromic features to confirm diagnosis and identify specific mutations 3
3. Family screening: First-degree relatives may require echocardiography and clinical evaluation when genetic syndromes are identified 3

Management Considerations

The underlying cause impacts treatment approach:

• Isolated pectus carinatum: May be managed with bracing for mild to moderate cases or surgical correction for severe cases 3
• Syndromic pectus carinatum: Requires comprehensive management of the underlying condition before addressing the chest wall deformity 3

Important Caveats

• The true incidence and prevalence of pectus carinatum are difficult to estimate due to lack of consensus on definition 1
• There is no direct correlation between the appearance of the deformity and clinical symptoms 6
• An interdisciplinary approach is strongly recommended for patients with additional symptoms beyond the chest wall deformity 2