Pathophysiology of Pectus Excavatum
Pectus excavatum develops primarily from abnormal overgrowth or growth disturbance of the costal cartilages, leading to posterior displacement of the sternum and anterior chest wall depression. 1, 2
Underlying Mechanisms
The pathogenesis centers on disruption in the maturation of the parasternal region during embryonic and fetal development 3. The leading hypothesis focuses on:
- Excessive or disordered growth of costochondral cartilages that pushes the sternum posteriorly 1, 2
- Disruption occurs during the maturation phase of rib and sternal development, though the exact trigger remains incompletely understood 3
Genetic Factors
Familial clustering strongly suggests genetic predisposition 4:
- Pectus excavatum occurs as an autosomal dominant trait in some families 4
- Association with FBN1 gene mutations has been documented in families with tall stature and pectus excavatum 4
- A novel FLNA gene variant (c.6616G>A; p.(Val2206Met)) was recently identified in a patient with severe pectus excavatum and myxomatous valvular disease 5
- Increased prevalence in connective tissue disorders including Marfan syndrome, where thoracic skeletal abnormalities like pectus excavatum commonly occur alongside straight thoracic spine 6, 7
Associated Syndromes and Conditions
Pectus excavatum frequently appears as part of broader connective tissue abnormalities:
- Marfan syndrome: Associated with defective fibrillin-1 microfibrils in the extracellular matrix 7, 8
- Bicuspid aortic valve sequence: Includes thoracic-cage deformity as part of variable expression 4
- MASS phenotype and other FBN1-related conditions 4
Physiologic Consequences
The structural deformity creates secondary effects:
- Mild reduction in lung volumes (typically within normal range) with mild air-trapping 9
- Evidence of lower airway obstruction in many patients 9
- Exercise intolerance primarily due to cardiovascular rather than pulmonary causes 9
- Cardiac compression can occur in severe cases, with rare reports of sudden cardiac death from ventricular fibrillation due to right coronary ostium compression 5
Clinical Caveat
The psychological impact often exceeds the actual physical effect 9. There is no direct correlation between the appearance of the deformity and clinical symptoms 10, making assessment challenging and emphasizing the need for objective evaluation beyond visual inspection.