STAT3 and Autoimmunity: Non-lethal effects include short stature, autoimmunity, and erythropoiesis defects,46 diagnosed at birth and persisting to adulthood.47–49 Many are the result of point mutations, often causing gain-of-function effects; the likely consequences of these include disruption to STAT3 function.35 We propose that these human post-natal growth defects may begin during early postimplantation development, resulting from the challenges imposed upon the epiblast to undergo rapid proliferation in preparation for gastrulation.