Diverse electrophysiological demyelinating features in a late-onset glycogen storage disease type IIIa case.

Glycogen storage disease type IIIa (GSD IIIa) is a rare etiology among patients with adult-onset myopathy, which is typically associated with axonopathy rather than demyelination. We report a genetically and pathologically confirmed case that exhibited prominent electrophysiological hallmarks of demyelination, including prolonged distal motor latency, temporal dispersion, prolonged F-waves, and conduction block. The presence of these diverse demyelinating characteristics in this context, excluding other factors, is infrequently reported, suggesting that glycogen accumulation may influence not only muscles but also potentially the myelin, thereby broadening our comprehension of this rare disease spectrum.