Endocardial fibroelastosis causing sudden death in an infant: Autopsy case report of an unusual lesion.

Endocardial fibroelastosis is characterized by proliferation of both elastic and collagenous fibers within the endocardium, causing diffuse or localized thickening. A four-and-a-half-month-old baby was admitted to a local hospital, with a history of seizures for one day. Baby developed features of heart failure and died within one week after admission. At the post-mortem examination, heart was found to be enlarged with dilated ventricles. The endocardium of left ventricle was markedly thickened with a whitish appearance. Histopathology showed a thick layer of collagenous fibrous tissue in the endocardium, which was confirmed by Masson trichrome stain. The cause of death was offered as dilated cardiomyopathy due to endocardial fibroelastosis. The underlying mechanisms of myocardial fibrosis remain unclear. It is hypothesized that genetic, infectious, inflammatory, and nutritional processes are involved in this condition. This case highlights the importance of gross specimen examination and special staining methods to support histopathology after postmortem examination, for ascertaining the cause of death.