Often called "pigeon breast," pectus carinatum is when the breastbone (sternum) looks like it is pushed out. Pectus carinatum occurs more often in males than females (4:1 ratio), and develops somewhat later in males than it does in females. It often gets worse as a child gets older and during growth spurts that occur during late childhood and adolescence.

Although pectus carinatum rarely interferes with overall health, it generally does not interfere with heart and lung function.