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Sarcoidosis has been reported to have a particular predilection for adults under the age of 40 years.w1 The incidence of sarcoidosis varies greatly by ethnicity and region, occurring in 3 to 20 per 100 000 for whites and 35.5 to 80 per 100 000 for blacks.1 Scandinavian populations have been reported as having a higher prevalence than other Caucasian regions.w2
The incidence of cardiac sarcoidosis (CS) also varies by the type of study performed, whether clinical or autopsy study, with clinical and autopsy reports ranging from 5–10% up to 27%, respectively.2 w3 Recently, Mehta et al observed almost 40% of patients with sarcoidosis had CS on advanced imaging (cardiac MRI or positron emission tomography (PET)).3
Pathogenesis of cardiac sarcoidosis
The aetiology of sarcoidosis remains unclear. Genetic, environmental, infectious, and immune dysregulation aetiologies have all been postulated.w4 Data from ACCESS (A Case-Control Etiologic Study of Sarcoidosis)4 indicated a relative risk of 4.7 for parents and siblings of sarcoid patients. While several genes or polymorphisms have been suggested,w5–w7 it is unlikely that sarcoidosis is a purely genetic disease. Rather, it may be a final common pathway of granulomatous disease caused by a heterogeneous group of agents in a genetically susceptible patient. The American Thoracic Society, the European Respiratory Society, and the World Association of Sarcoidosis and Other Granulomatous Disorders5 define sarcoidosis as a multisystem disorder of unknown cause.
The cardiovascular system is the third most frequently involved organ system in patients with sarcoidosis.w8 All parts of the heart can be affected, with the left ventricular free wall being the most common location (figure 1).6 The cardiac conduction systemw9 is also commonly affected. The hallmark of sarcoidosis is the presence of non-caseating, non-necrotising, granulomas (figure 2).7 w10 w11