Mixed-type Cardiomyopathy with Severe Systolic Dysfunction: An Uncommon Presentation of Pompe Disease

Introduction: Literature about mixed-type cardiomyopathy in Pompe disease is scarce. We present the case of an infant with severe eccentric, asymmetric hypertrophic cardiomyopathy successfully treated with enzyme replacement therapy (ERT) and high-dose β-blockers.

Methods: A 5-week-old girl was admitted because of weight decline and rapid breathing. Echocardiogram showed impaired systolic function (FS 15%), eccentric hypertrophy without cavity obstruction and posterior and lateral left ventricular non-compaction. IVS thickness was 6.6 mm (z +2.65), LV diastolic diameter 35 mm (z + 5.88), LV mass index was severely abnormal at 164 g/m². NT-proBNP was at 32,000 pg/mL, E/E′ ratio 36. The patient started heart failure treatment with diuretics. Regaining systolic function and no longer on respiratory distress, the patient then was carefully started on β-blockade with Propranolol with a final range of 6–8 mg/kg/d. Initial diagnostics including genetic testing was unremarkable. Meanwhile, the patient had become floppy, showing head lag. The diagnostic work-up 6 weeks later finally showed a severe deficiency of acid α-glucosidase as in Pompe disease (Type II glycogen storage disease). The IVS now measured 15 mm (z + 6.4). The patient was immediately started on ERT with high-dose Myozyme™ (40 mg/kg once a week).

Results: At the age of 27 months, the patient is still on ERT and Propranolol. She walks independently and has normal muscle tone. There was gradual improvement in left ventricular hypertrophy and function. At the most recent follow-up IVS was 7 mm (z + 2.19), LV diastolic diameter 29mm (z + 0.92), LV mass index moderately abnormal at 112 g/m² and E/E′ ratio 11.

Conclusion: Despite the initial presentation as a mixed-type cardiomyopathy with severe systolic dysfunction, the clinician has to have a high awareness of Pompe disease in infants with cardiomyopathy, especially when signs of myopathy emerge. Enzyme replacement therapy and high-dose Propranolol treatment in infants with Pompe disease with this uncommon type of cardiomyopathy seems feasible.