Kounis syndrome and hypersensitivity myocarditis - One and the same? Insights from cardiac magnetic resonance imaging.

Myocarditis and acute coronary syndrome are both described in the setting of concurrent hypersensitivity reactions to a variety of allergenic triggers (hypersensitivity myocarditis and Kounis syndrome respectively). Mast cell degranulation is thought to be pivotal in the pathogenesis of both clinical entities. Cardiac magnetic resonance imaging (CMR) has assumed a key role in the assessment of chest pain syndromes, providing a useful non-invasive tool to aid clinical decision-making. Despite increasing availability and uptake of CMR, only a small fraction of published Kounis syndrome cases report CMR findings, and confirmation of myocardial infarction remains elusive. We present a case of presumed Kounis syndrome with comprehensive CMR imaging that provides an insight into why these two well-described clinical entities share many clinical features - perhaps they are one and the same. <Learning objective: Myocarditis and acute coronary syndrome (ACS) in the setting of hypersensitivity reactions share similar clinical characteristics. Endomyocardial biopsies are often not undertaken in this patient group, and differentiation has typically been at the clinicians' discretion. Cardiac magnetic resonance imaging can provide an insight into the underlying pathogenesis, with currently available evidence suggesting myocarditis is a prerequisite for ACS, rather than being stand-alone clinical entities.>.