Primary idiopathic endocardial fibroelastosis in a four-month-old infant: Case report and brief literature review

Primary idiopathic endocardial fibroelastosis (pEFE) is a rare infantile cardiomyopathy characterized by diffuse thickening of the ventricular endocardium by collagen and elastic tissue, leading to severe left ventricular dysfunction. This report describes a four-month-old male infant who presented with a three-week history of feeding difficulties, failure to thrive, and respiratory distress, which were initially misdiagnosed as gastroesophageal reflux. An acute episode of perioral cyanosis prompted emergency evaluation revealing profound left ventricular dilation and a severely reduced ejection fraction of 28%. Following the exclusion of anomalous left coronary artery from the pulmonary artery (ALCAPA) and other secondary causes via echocardiography and cardiac magnetic resonance imaging, an endomyocardial biopsy confirmed the diagnosis of pEFE. 
The infant was managed with intensive anti-heart failure pharmacotherapy, including captopril, carvedilol, furosemide, and spironolactone, alongside aggressive nutritional support. This medical regimen resulted in significant clinical improvement, with the ejection fraction recovering to 55% at the 18-month follow-up, despite persistent endocardial echogenicity. 
This case underscored the critical importance of maintaining a high index of suspicion for underlying cardiomyopathies in infants presenting with persistent feeding difficulties and respiratory symptoms, as early diagnosis and aggressive medical management can yield excellent long-term outcomes and reverse profound cardiac dysfunction in primary endocardial fibroelastosis (EFE).