Kounis Syndrome Features in Special Populations.

Kounis syndrome (KS) describes the occurrence of acute coronary syndromes precipitated by allergic, hypersensitivity, or anaphylactic reactions and represents a unique intersection between immunologic activation and cardiovascular disease. The epidemiology of KS is likely underestimated due to diagnostic overlap with other cardiac and allergic conditions and limited awareness across medical specialties. This narrative review focuses on the distinctive features of KS in special populations, emphasizing how patients' age, comorbidities, immune status, and vascular substrate modify presentation, diagnosis, and outcomes. In elderly patients, polypharmacy, increased plaque vulnerability, and endothelial dysfunction favor Type II and III KS. Pediatric cases, although rare, are predominantly Type I and strongly associated with food allergies, insect stings, vaccines, and antibiotics, with under-recognition driven by diagnostic bias and ethical concerns surrounding invasive testing. Patients with coronary stents, cardiac devices, chronic kidney disease, and those receiving dialysis exhibit heightened susceptibility due to chronic inflammation, foreign-body hypersensitivity, and prothrombotic states. Pregnancy and the peripartum period represent a unique immuno-hemodynamic milieu in which Th2 immune shift, increased coronary vasoreactivity, and obstetric triggers can compromise both maternal and fetal perfusion. Additional risk modulation is observed in atopic individuals, asthmatics, patients with autoimmune, inflammatory, oncologic, psychiatric, and neurodevelopmental conditions, as well as in COVID-19 and post-infectious states. We propose a host-modified framework for KS that complements traditional classification by integrating immune phenotype and vascular substrate, enabling improved risk stratification and personalized preventive strategies.