Cardiomyopathy of glycogen storage disease type III.

To identify the severity of cardiac involvement in glycogen storage disease type III (GSDIII), and its relation to skeletal muscle involvement and age, 23 patients were studied. The median age was 10 years. Echocardiography, electrocardiography, and creatine phosphokinase (CK) levels were used to assess cardiac and skeletal muscle involvement. Septal and left ventricular posterior wall measurements were compared with normal data. Shortening fraction was derived from left ventricular cavity dimensions. In some patients the echocardiogram resembled that of hypertrophic cardiomyopathy. Thirteen of 20 electrocardiograms (ECG) were abnormal. Eleven patients had septal and/or posterior wall thickness > 95% confidence limits (CL). Despite this, cardiac symptoms were uncommon. The CK levels were not directly associated with cardiac abnormalities. Older patients (> 20 years) had more abnormal measurements of posterior wall thickness than did younger ones (< 20 years). This finding, albeit in a cross-sectional series, suggests progressive myocardial involvement with age despite the absence of symptoms.