Glycogen storage disease type III (GSD III) may present with hepatic disease or may involve both skeletal and cardiac muscles as well. To assess the prevalence of neuromuscular and cardiac involvement in a group of children with GSD III, 28 children with GSD III, diagnosed by enzymatic assay, were enrolled in the study after an informed consent was obtained from their parents/guardians and after the study protocol was approved by our institutional ethical committee. Their mean age was 6.6 + 3.1 years. All cases were assessed neurologically by clinical examination, electromyography (EMG), and nerve conduction velocity. The heart was examined clinically by electrocardiogram and echocardiography. Seventeen patients (61 %) had myopathic changes by EMG, three of them had associated neuropathic changes. Creatine phosphokinase (CPK) was elevated in all myopathic cases except one. Children with myopathic changes were significantly older (p = 0.02), and CPK was significantly higher (p < 0.0001). Nine cases had left ventricular (LV) hypertrophy, seven of them had myopathic changes by EMG.

Conclusion: Myopathic changes are not uncommon in children with GSD III. Myopathic changes tend to occur in older age and are associated with higher CPK level. Cardiac muscle involvement is less common in this age group and may, on occasion, occur alone without skeletal muscle involvement. Despite mild degrees of affection in this age group, it is recommended to perform prospective annual screening using EMG and echocardiography in order to augment dietary therapy regimen to prevent progression to life threatening complications.