Anterior chest wall deformity is the result of the abnormal and unequal growth of the costal cartilages that connect the breast bone (sternum) to the ribs.

This can cause a sunken or hollow appearance which is called Pectus Excavatum or a prominence of the front of the chest called Pectus Carinatum. Although these are the most common presentations, occasionally more complex presentations can occur. Anterior chest wall deformities can be present at birth or develop as a child grows often rapidly progressing during puberty.