Pectus, or a chest wall defect, is an abnormality in the structure of the chest caused by uneven growth of the cartilage that connects the ribs. Dr. Anderson explains, “While the exact cause or etiology of pectus defects is unclear, it’s quite common. Pectus excavatum, or sunken chest, affects about one in 400 children. Pectus carinatum, or pigeon chest, affects about one in 500 children. Both types are more commonly found in males than females and it can run in families.”