The electrodiagnostic characteristics of Glycogen Storage Disease Type III.

PURPOSE: Glycogen Storage Disease Type III, also known as debrancher deficiency or Cori disease, is an autosomal recessive disorder recognized for both its hepatic and muscle manifestations. The neuromuscular manifestations of Glycogen Storage Disease Type III are not well characterized. In this study, we attempt to better define the disorder.

METHODS: The medical records of 40 patients with Glycogen Storage Disease Type III seen at Duke University during 1990-2009 were reviewed. The medical records of all patients with nerve conduction studies and/or electromyography were examined.

RESULTS: Twelve patients with Glycogen Storage Disease Type III (aged 5-55 years) had undergone nerve conduction studies +/- electromyography. Three of these cases are presented in detail. Nine patients had Glycogen Storage Disease Type IIIa, two patients had Glycogen Storage Disease Type IIIb, and the clinical subtype of one patient was unknown. All had nerve conduction studies and of those nerves tested, abnormalities in the median motor response were most common, corresponding to previously described, intrinsic hand muscle weakness. Electromyography was performed in eight patients and myopathic findings were present in six individuals. Abnormal electrodiagnostic findings were more common in older patients. The two patients with Glycogen Storage Disease Type IIIb had electrodiagnostic evidence of nerve involvement with minor myopathic findings.

CONCLUSIONS: The neuromuscular manifestations of Glycogen Storage Disease Type III include myopathy and neuropathy and are more likely to occur with increasing age, even in those diagnosed with Glycogen Storage Disease Type IIIb. Intrinsic hand muscle weakness is likely due to a combination of nerve and muscle dysfunction, a finding that may have implications for treatment.