Recently, a connection between the BRAF mutational status and a specific phenotype was described; however, no studies have yet evaluated the correlations between other mutations and the clinical features of the disease.<h4>Objectives</h4>This study aims to clarify the association between the clinical phenotype and genetic mutations identified in the neoplastic cell lines of ECD.<h4>Methods</h4>We describe a case of ECD characterized by pericardial involvement and a KRAS mutation shared with chronic myelomonocytic leukemia. The gene discussed is BRAF; the disease is familial atrioventricular septal defect.