Centronuclear Myopathy with Unusual Presentation of Electrical Myotonia and Supraventricular Tachycardia: Report of a Case

Centronuclear myopathy is associated infrequently with cardiomyopathy. We present a sporadic case of a 20-year-old young male with mild frontal baldness, facial weakness, and bilateral ptosis, as well as weakness and muscle wasting involving the neck, limb girdles and limbs. ECG showed paroxysmal supraventricular tachycardia during palpitation episode. Echocardiography showed prolapse as well as thickness of anterior leaflet of mitral valve, left ventricle generalized hypokinesia, and mild left ventricular systolic dysfunction. EMG study displayed myotonia-like discharges. Muscle biopsy showed high frequency of central nuclear fibres in both main fibre types and type 1 fibre atrophy. We conclude that myotonia-like discharges on the EMG and cardiac arrhythmia may resemble characteristics of myotonic dystrophy, and may lead to an erroneous diagnosis of myotonic dystrophy.