(Top) Family pedigree. Arrow = proband; * = died of nonobstructive HC, but echocardiographic images were not available for review; + = gene positive; − = gene negative; solid symbols = HC phenotype; symbol with slash = died; patient ages appear in parentheses. ( Bottom) Two-dimensional echocardiographic demonstration of diverse phenotypic expressions of HC in related patients due to troponin T mutation (c487_489delGAG). (A) Patient III.4—a 37-year-old asymptomatic man with nonobstructive HC and hypertrophy of anterior ventricular septum (*) (23 mm); ejection fraction 53%. (B) Patient III.2—a 28-year-old woman with nonobstructive HC and predominant hypertrophy of posterior ventricular septum (*) (21 mm); ejection fraction 75%. (C) Patient II.1—a 57-year-old man with progressive heart failure (and 2 prior cardiac arrests) with heart transplant for end-stage HC at age 54, ejection fraction 30%; LV end-diastolic dimension 52 mm; left atrial enlargement (transverse dimension, 58 mm); VS thickening (white line) is mild (16 mm). (D) Patient II.5—a 67-year-old woman with severe heart failure and transplant at age 61, showing a distinctly different and unusual expression of HC with markedly enlarged atria and restrictive physiology; LV wall thickness was normal (9 mm); (arrow) unchanged over 30 years of observation; ejection fraction 40%. Myocardial fibrosis was absent by contrast CMR and examination of the explanted heart although myocyte disarray was reported by histopathology. LA = left atrium; RA = right atrium; RV = right ventricle; VS = ventricular septal.