Introduction: We report a patient with acid maltase deficiency who presented with subacute respiratory failure as the first symptom without significant extremity weakness.
Methods and results: Electromyography of extremities was normal but showed myopathic changes and myotonic discharges limited to axial muscles only. Muscle biopsy confirmed the diagnosis.
Conclusion: It is essential to examine axial muscles during electromyography if a patient presents with respiratory failure of unclear etiology even if the clinical examination does not show significant weakness in the extremities and electromyographic findings in the extremities are unremarkable.