A 60-year-old woman with weakness, fatigue, and acute respiratory failure: case report and discussion of the differential diagnosis.

A 60-year-old woman with chronic progressive fatigue, diurnal somnolence, proximal muscle weakness, and dyspnea developed acute respiratory failure when given supplemental oxygen. Hypoventilation secondary to neuromuscular dysfunction was suspected by the critical care specialist. Neurologic consultation and supportive laboratory evaluations led to the diagnosis of acid maltase deficiency, which was confirmed by muscle biopsy. The discussion includes a literature review that describes the pathophysiology and treatment of this rare muscle enzyme deficiency disorder. Acid maltase deficiency should be suspected in any adult presenting with hypoxemia, fatigue, and acute respiratory failure.