C. diphtheriae, Corynebacterium ulcerans, and Corynebacterium pseudotuberculosis species possess the tox gene necessary for diphtheria toxoid production; the toxin exhibits robust cytotoxicity, entering respiratory mucosal cells via receptor‐mediated endocytosis to inhibit protein synthesis and induce cytolysis [4], followed by rapid dissemination of the toxin into circulation. The gene discussed is TOX; the disease is diphtheria.