Often called "pigeon breast," pectus carinatum is caused when the sternum (breastbone) is pushed outward. The forward protrusion of the sternum often causes pain during exercise or during times of increased respiratory effort. Pectus carinatum occurs more frequently in males than females (4:1 ratio), and develops somewhat later in males than it does in females. It often increases in severity with age and generally worsens during growth spurts that occur during late childhood and adolescence.
Although pectus carinatum occasionally interferes with overall health, it generally does not interfere with cardiorespiratory (heart and lung) functioning.