Fibromuscular dysplasia of coronary arteries resulting in myocardial infarction associated with hypertrophic cardiomyopathy in Noonan's syndrome.

The first autopsy case of fibromuscular dysplasia in the coronary arteries associated with hypertrophic cardiomyopathy in Noonan's syndrome is reported. A 16-month-old female infant with no significant family history was diagnosed with Noonan's syndrome and subsequently died of cardiac and respiratory failure. Autopsy revealed cardiac hypertrophy, atrial septal defect, and scar lesions in the left ventricle and ventricular septum. Histologically, the myocardium exhibited myocardial fiber disarray, which was indicative of hypertrophic cardiomyopathy. The main trunks of the coronary arteries showed protuberant intimal thickening with interruption of the internal elastic lamina. Intramyocardial coronary arteries also exhibited various degrees of irregular intimal proliferation and diffuse fibrous thickening of the adventitia. These arterial lesions were consistent with fibromuscular dysplasia. Small arteries around the scar showed remarkable stenoses, which probably led to myocardial ischemia. The fibromuscular dysplasia in this case was considered to arise as a cardiovascular disorder in conjunction with Noonan's syndrome.