This explains his favourite motto: "Pectus est quod theologum facit."
Pectus excavatum is a malformation of the chest in which the child's breastbone, or sternum, is sunken inward.
Although pectus carinatum does not cause breathing difficulties, it can cause embarassment about appearance.
A few children with Marfan may have a pectus excavatum on one side of their chest and a pectus carinatum on the other.
Pectus excavatum and pectus carinatum can be treated by surgery.