It is called Pectus excavatum. Long work, I know. It is a deformation in the chest that makes it sink in like a bowl. The bones do that, sometimes they press against the lungs and can make it difficult of breath and you must be careful when lifting.
Now, mine is not bad at all according to the doctors. I have mild persistent asthma but it is not caused by this either... Luckily my Fiance finds it attractive in me for some reason...
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I have the opposite, I have a little bump right below my left pectoral.