Kounis syndrome is the concurrence of acute coronary syndromes with conditions associated with mast cell activation, such as allergies or hypersensitivity, and anaphylactic or anaphylactoid insults. In this report, we present a case of a patient who suffered a Kounis syndrome after a metamizole infusion in post-surgery time. NSAIDS are the most frequent causes of drug associated anaphylactic reactions in literature. The cardiac manifestations of systemic mastocytosis may be lifethreatening, and for this reason is important to consider their presence and to predefine the way to treat it.