Description of a new clinical syndrome: thoracic constriction without evidence of the typical funnel-shaped depression—the "invisible" pectus excavatum oleh Anna Hohneck, Uzair Ansari, Michèle Natale, Karsten Wittig, Daniel Overhoff, Philipp Riffel, Michael Boettcher, Ibrahim Akin, Daniel Duerschmied, Theano Papavassiliu