[A case of myotonic dystrophy associated with intracardiac conduction abnormalities and aortic regurgitation]

A rare case of myotonic dystrophy with mechanical derangement in a 48-year-old male is reported. The patient was admitted to Fuzisawa City Hospital because of chest discomfort. On physical examination, he had the typical facial appearance of myotonic dystrophy, and displayed grip myotonia. The blood pressure was 120/60 mmHg and the pulse 51, regular. A systolic ejection murmur at the cardiac base, an early diastolic blowing murmur along the left sternal border, and a pansystolic murmur at the apex were heard. The deep tendon reflexes were all normal. Elevation of serum creatine kinase and aldolase were noted. Chest X-ray films suggested moderate cardiomegaly. An electrocardiogram showed sinus bradycardia, atrioventricular block and left bundle branch block, suggesting diffuse involvement of the conduction system. An echocardiography confirmed the presence of left ventricular enlargement, thickened aortic valves, mitral regurgitation, and aortic regurgitation. Selective coronary angiography revealed no abnormalities. Left ventriculography demonstrated diffuse hypokinesis of the entire ventricle. Light microscopy of biopsied right myocardium revealed prominent interstitial fatty infiltration, mild interstitial fibrosis, and variation in the nuclear size. A 22-year-old son also had myotonic dystrophy and had an echocardiography indicative of thickened valves with aortic regurgitation. Myotonic dystrophy is a autosomal dominant disease. Cardiac involvement selectively disturbs the conduction system, sinus node, and to a lesser extent myocardium. Although the presence of aortic regurgitation could be a mere coincidence, we believe that this did not occur by accident, because the patient's son also had aortic regurgitation.