Pectus excavatum
Pectus excavatum is a congenital medical condition where the ribs and sternum grow abnormally, producing a sunken appearance to the chest. This makes the chest look  like it has caved in on itself.  It is also commonly referred to as "funnel chest" or "chest bowl". It is the most common form of pectus deformity, occurring in approximately 1 in 300-400 births, with a 3:1 male predominance ratio. While Pectus Excavatum occurs at birth, it often does not develop properly until early adolescence when growth is more rapid.