Pectus Excavatum and Pectus Carinatum

GENESIS

Pectus excavatum and pectus carinatum are the most common abnormalities of the thorax. The incidence of pectus excavatum is between 1 and 8 per 1000 persons, and pectus carinatum is two to four times less frequent than pectus excavatum, with a significant male-to-female excess for both pectus carinatum and pectus excavatum. If no features of an underlying disorder are detected, then the pectus abnormality is considered to be an isolated abnormality. Although cases of nonsyndromal pectus excavatum or carinatum with a positive family history fitting mendelian inheritance have been described, no single gene has been identified as a causative factor for either deformity, and the recurrence risk for a nonfamilial isolated pectus deformity appears to be low. If other features are present, then appropriate further diagnostic studies are indicated because pectus excavatum or carinatum can be part of many syndromes. The most frequently observed monogenic syndromes with pectus abnormalities are Marfan syndrome ( Fig. 19.1 ) and Noonan syndrome ( Fig. 19.2A ).

Pectus excavatum or carinatum can be present at birth, but both disorders are usually not recognized until early childhood, when the deformity progresses ( Fig. 19.2B ). The cause of each condition is not known with certainty, but pectus excavatum is thought to result from an inward overgrowth of costal cartilages, which becomes more apparent during the period of rapid skeletal growth in early adolescence. Pectus carinatum is thought to be caused by abnormal outward growth of costal cartilages with precocious fusion of sternal growth plates, resulting in anterior bowing of the superior costal cartilages and consequent protrusion of the superior portion of the sternum. Most recent studies agree that the primordial defect leading to deformation of the anterior chest wall is related to the costal hyaline cartilage structure and function, and the origin of pectus deformities may be found in the ultrastructure of the costal cartilage. A positive family history is observed in 43% of pectus excavatum cases and 25% of pectus carinatum cases, and the mean prevalence of adolescent idiopathic scoliosis in patients with pectus deformity is 13.1%. This association may represent the occurrence of a common underlying condition, and abnormal skeletal growth in a variety of skeletal dysplasias and genetic connective tissue disorders can result in pectus deformities, which are especially frequent in patients with Marfan syndrome. Pectus deformities affect a significant proportion of the general population (0.8%) and an even greater proportion of patients with Marfan syndrome (up to 70%). Pectus excavatum can be a clue to the early diagnosis of Morquio syndrome, a rare autosomal recessive type of mucopolysaccharidosis that can take several years (mean 2.6 years) from initial presentation to definitive diagnosis (mean age 4.7–4.9 years). Since enzyme replacement is available, late diagnosis complicates disease management. These authors reported a case of Morquio A syndrome in which definitive diagnosis was made within 2 months of initial presentation.

Chest wall deformities can be divided into two main categories, congenital and acquired. Congenital chest wall deformities may present any time between birth and early adolescence. Acquired chest wall deformities typically follow prior chest surgery or a posterolateral diaphragmatic hernia repair (Bochdalek). Open thoracotomy for repair of cardiovascular defects during early childhood sometimes affects the growth of costal cartilages, leading to pectus deformities with secondary associated scoliosis. Large congenital diaphragmatic hernias can be repaired with either a muscle flap or prosthetic patch. Prospectively, 75% of flap patients and 67% of patch patients had pectus, and 13% of flap patients and 33% of patch patients had scoliosis. The operative technique did not appear to affect the incidence of subsequent skeletal deformity.