Dilated Form of Endocardial Fibroelastosis as a Result of Deficiency in Respiratory-Chain Complexes I and IV

Abstract

A 2-month-old girl with poor appetite and failure to thrive was admitted because of pallor, dyspnea, and tachycardia with periodic gallop rhythm. Chest x-ray (Figure 1) showed cardiomegaly, and echocardiography (Figure 2) revealed left ventricular dilation (diastolic diameter, 41.5 mm [normal, <23 mm]), decreased contractility, and mild to moderate mitral valve insufficiency. ECG (Figure 3) showed sinus rhythm with left bundle-branch block and repolarization abnormalities. These findings were compatible with severe dilated cardiomyopathy. Polymerase chain reaction of the serum failed to detect any cardiotropic virus genomes. There was lactic acidosis. On frozen striated muscle, the mitochondrial respiratory chain function was tested and found to have decreased activities of complexes I (NADH coenzyme Q reductase, 9.1 nmol/min per milligram [normal, 13 to 24]) and IV (cytochrome- c oxidase, 103 nmol/min per milligram [normal, 120 to 220]). Therapy with oxygen, digoxin, captopril, and furosemide was initiated. Despite this, her cardiovascular function continued to worsen; she was readmitted at 10 months of age for decompensated heart failure and died 8 days later. Her family history revealed 1 brother who had died suddenly at the age of 3 months (no autopsy was performed). Figure 1. Chest x-ray obtained at age 2 months showing significant enlargement of the cardiac profile. Figure 2. Transthoracic echocardiography performed at the same age displaying severe left ventricular (LV) chamber dilation. RV indicates right ventricle; LA, left atrium; and Ao, aorta. Figure 3. ECG obtained at first admission to the hospital showing left bundle-branch block and repolarization abnormalities. Autopsy confirmed cardiac enlargement with severe left ventricular chamber dilation (Figure 4A); the endocardium was whitish and …