Endocardial fibroelastosis

**Definition:** Endocardial fibroelastosis is the formation of a marked fibro-elastic thickening of the subendocardium in one or both cardiac ventricles. A disorder of fetuses and infants, secondary causes include congenital left-sided obstructive cardiac lesions, metabolic disorders, autoimmune disease (anti-Ro/anti-La antibodies), and transplacental viral infection such as mumps. Primary endocardial fibroelastosis has been linked to recessive and x-linked inheritance, such as with Barth syndrome.