Diagnosis of Pectus Carinatum
Pectus carinatum is diagnosed primarily through clinical inspection of the anterior chest wall, identifying asymmetric or symmetric protrusion of the sternum and adjacent costal cartilages, followed by mandatory cardiac evaluation and genetic syndrome screening. 1
Clinical Inspection and Physical Examination
The diagnosis begins with visual inspection of the anterior chest wall in pubertal adolescents, documenting whether the sternal protrusion is symmetric or asymmetric. 1 The deformity is characterized by anterior protrusion of the sternum and adjacent costal cartilages, creating a "keel chest" appearance. 2
Key Physical Findings to Document:
- Type of deformity: symmetric (most common), asymmetric, or mixed (ipsilateral carinatum with contralateral excavatum) 3
- Associated musculoskeletal abnormalities: scoliosis (present in 23% of cases), hyperlordosis, kyphosis, or vertebral anomalies 3
- Dysmorphological features: joint hypermobility, skin hyperextensibility, and arachnodactyly suggesting Marfan syndrome 1
Important clinical pitfall: The deformity is often not identified until after age 11 years in approximately half of patients, despite being present earlier. 3
Mandatory Cardiac Evaluation
Complete cardiac evaluation with echocardiography is mandatory in all patients with pectus carinatum, as this deformity may indicate underlying genetic syndromes. 1, 4 The American College of Cardiology rates this recommendation with high strength of evidence. 1
Echocardiographic Assessment Must Include:
- Aortic root dilation (particularly important in Marfan syndrome) 1
- Mitral valve prolapse (prevalence 10-20% in pectus deformities with connective tissue syndromes) 1, 5
- Congenital heart defects 1
- Pulmonary valve stenosis (especially in Noonan syndrome patients) 5
- Right ventricular size and function to assess for compression effects 5
Pulmonary Function Assessment
Pulmonary function testing is recommended when the child can cooperate (typically age 5+), as up to 60% of patients develop restrictive lung disease. 1 The American Thoracic Society recommends this assessment with moderate strength of evidence. 1
Specific PFT Parameters to Evaluate:
- Forced vital capacity (FVC) reduction 1
- FEV1/FVC ratio abnormalities 1
- Restrictive pattern affecting primarily the lateral thorax rather than anterior-posterior dimension 1, 5
Genetic Syndrome Screening
The National Society of Genetic Counselors recommends screening for Marfan syndrome and Noonan syndrome, as these are the most frequently observed monogenic conditions associated with pectus carinatum. 1
Screening Algorithm:
- Marfan syndrome assessment: Pectus carinatum scores 2 points in the systemic features scoring system (sensitivity 80-90%) 1
- Family history: Document chest wall deformities (present in 26% of cases) and scoliosis (12% of cases) 3
- Associated conditions to evaluate: Homocystinuria, Morquio syndrome, osteogenesis imperfecta, Noonan syndrome, and mitral valve prolapse 2
Imaging Studies
CT imaging with the improved Haller index can be used for objective severity assessment and surgical planning, though it is not required for initial diagnosis. 6 The measurement is performed on the axial CT slice where the most convex thorax presents, with normal chest ratio being 2.56 and pectus carinatum patients averaging 1.73. 7
When to Order Advanced Imaging:
- MRI or CT: For surgical planning if intervention is considered 1
- CT with IV contrast: When precise anatomic measurements are needed for surgical reconstruction 5
Critical caveat: Unlike pectus excavatum, the diagnosis of pectus carinatum relies primarily on clinical inspection rather than imaging, as the protrusion is readily apparent on physical examination. 1, 3