The juvenile form of Pompe disease is MOST often associated with which of the following clinical abnormalities?
- □ (A) Micrognathia
- □ (B) Hypertrophic cardiomyopathy
- □ (C) Hypertonia
Pompe disease is a disorder of carbohydrate metabolism and one of several glycogen storage diseases. The defective enzyme (acid α-glucosidase) impedes the breakdown of glycogen into glucose, thus impairing gluconeogenesis. The enzyme is located in cellular lysosomes, particularly heart and skeletal muscle. Left untreated, glycogen deposits accumulate in end organs, specifically the heart and skeletal muscles, which can result in cardiomegaly and congestive heart failure, skeletal muscle weakness, and hypotonia.
The infantile form of Pompe disease (Figure) presents early in life with congestive heart failure and death before age 2 years. The juvenile form of Pompe disease presents with significant weakness of skeletal and respiratory muscles. Another feature of the juvenile form is cardiac hypertrophy and subaortic stenosis, as well as enlargement and protrusion of the tongue, possibly making intubation difficult. Macroglossia, rather than micrognathia, is associated with Pompe disease. Death usually occurs in the second or third decade of life. The adult form of Pompe disease is milder, with gradual onset of limb girdle weakness.
Large glycogen deposits in the heart can also lead to thickening of the intraventricular septum and hypertrophic cardiomyopathy (HCM). When patients with HCM develop tachycardia and low afterload conditions, a dynamic left ventricular outflow tract (LVOT) obstruction may develop. The dynamic outflow obstruction can cause the anterior leaflet of the mitral valve to become entrained into the high velocity LVOT flow, leading to systolic anterior motion (SAM) and severe mitral regurgitation. The cycle of low afterload, tachycardia, dynamic LVOT obstruction, SAM, mitral regurgitation, and worsening hypotension can end with severe hemodynamic instability. Administration of a pure vasoconstrictor will help to boost systemic vascular resistance, slow the heart rate, reduce the LVOT dynamic outflow obstruction, minimize SAM, decrease the severity of mitral regurgitation, and return the patient to a more stable hemodynamic state.
Answer: B