Pectus carinatum, also called pigeon chest, is a malformation of the chest characterized by a protrusion of the sternum and ribs. It is distinct from the related malformation pectus excavatum. Signs and symptoms People with pectus carinatum usually develop normal hearts and lungs, but the malformation may prevent these from functioning optimally. In moderate to severe cases of pectus carinatum, the chest wall is rigidly held in an outward position. Thus, respirations are inefficient and the individual needs to use the accessory muscles for respiration, rather than normal chest muscles, during strenuous exercise. This negatively affects gas exchange and causes a decrease in stamina. Children with pectus malformations often tire sooner than their peers due to shortness of breath and fatigue. Commonly concurrent is mild to moderate asthma. Some children with pectus carinatum also have scoliosis (i.e., curvature of the spine). Some have mitral valve prolapse, a condition in which the heart mitral valve functions abnormally. Connective tissue disorders involving structural abnormalities of the major blood vessels and heart valves are also seen. Although rarely seen, some children have other connective tissue disorders, including arthritis, visual impairment and healing impairment. Apart from the possible physiologic consequences, pectus malformations can have a significant psychologic impact. Some people, especially those with milder cases, live happily with pectus carinatum. For others, though, the shape of the chest can damage their self-image and confidence, possibly disrupting social connections and causing them to feel uncomfortable throughout adolescence and adulthood. As the child grows older, bodybuilding techniques may be useful for balancing visual impact. A less common variant of pectus carinatum is pectus arcuatum (also called type 2 pectus excavatum, chondromanubrial malformation or Currarino–Silverman syndrome or pouter pigeon malformation), which produces a manubrial and upper sternal protrusion, particularly also at the sternal angle. Pectus arcuatum is often confused with a combination of pectus carinatum and pectus excavatum, but in pectus arcuatum the visual appearance is characterized by a protrusion of the costal cartilages and there is no depression of the sternum. Causes Pectus carinatum is an overgrowth of costal cartilage causing the sternum to protrude forward. It primarily occurs among four different patient groups, and males are more frequently affected than females. Most commonly, pectus carinatum develops in 11-to-14-year-old pubertal males undergoing a growth spurt. Some parents report that their child's pectus carinatum seemingly popped up overnight. Second most common is the presence of pectus carinatum