We report the successful perioperative management of a patient with presumed mastocytosis undergoing pulmonary embolectomy. Postoperatively the patient went into vasodilatory shock, which was partly attributed to mast cell mediator release. H1- and H2-antagonists, steroids, and a single dose of methylene blue were given with improvement of hemodynamics. The patient was weaned off vasoactive substances and extubated by postoperative day 2. We discuss the perioperative management of patients with mastocytosis, briefly review the literature concerning anesthetic management for cardiac surgery in patients with this disorder, and discuss our patient’s alternative but related diagnosis of idiopathic mast cell activation syndrome.