The initial diagnosis for ECD for this branch of histiocytosis involves a thorough physical examination supported with lab tests, additional diagnosis of ECD involves the biopsy of tissue and analysis of the histiocytosis present in them, the histiocytes are typically foamy (histiocytes contain wastes from other cells present in them) and contain CD68 + and CD1a − which set them apart from other types of histiocytosis [51, 52]. The gene discussed is CD1A; the disease is familial atrioventricular septal defect.