A grandmother brings her 13-year-old grandson to you for evaluation. She noticed last week when he took off his shirt that his breastbone seemed collapsed. He seems embarrassed and tells you that it has been that way for quite awhile. He states he has no symptoms from it and he just tries not to take off his shirt in front of anyone. He denies any shortness of breath, chest pain, or lightheadedness on exertion. His past medical history is unremarkable. He is in sixth grade and just moved in with his grandmother after his father was deployed to the Middle East. His mother died several years ago in a car accident. He states that he does not smoke and has never touched alcohol. On examination you see a teenage boy appearing his stated age. On visual examination of his chest you see that the lower portion of the sternum is depressed. Auscultation of the lungs and heart are unremarkable.
What disorder of the thorax best describes your findings?
A) Barrel chest.
B) Funnel chest (pectus excavatum).
C) Pigeon chest (pectus carinatum).
D) Thoracic kyphoscoliosis.

Pectus excavatum, also known as Funnel chest, is a type of structural deformity of anterior thoracic wall. It is characterized by an abnormal shape of the sternum and the rib cage which gives the characteristic sunken or caved-in appearance of the sternum of the chest. This deformation can occur during puberty or present at the time of birth and can lead to impaired respiratory and cardiac functions and can also cause pain in the chest and the back.