Initial Therapy Response of 6 Months of Enzyme Replacement Therapy in 11 Juvenile/Adult M. Pompe Patients

Abstract

M. Pompe (acid maltase deficiency) is a lysosomal storage disorder leading to progredient heart failure and muscular weakness. In the most severe—that is, the infantile form—children present with cardiomyopathy, extreme muscular hypotonia, and early respiratory failure. They normally die in the first year of life. Adult patients present clinically with skeletal muscular weakness and/or respiratory failure due to insufficiency of the diaphragm muscle. In the medical literature, standardized studies are available only of infantile-onset Pompe disease patients. The age of our patient cohort ranged from 4 to 63 years (N = 11; mean [SD], 32.5 [18] years). In our standardized Pompe disease protocol, we performed lung function tests in the upright and supine positions, as well as the 6-minute walk test, before and 6 months after the start of enzyme replacement therapy (ERT) with alglucosidase alfa (20 mg/kg body weight every other week). As a parameter for lung function, we analyzed the forced vital capacity (FVC). All values were corrected for age, weight, and length, especially in children. Weakness of the diaphragm muscle was defined as loss of >20% of FVC in the supine compared with the upright position. The mean (SD) FVC in the upright position increased from 2.35 (1.06) L before ERT to 2.53 (1.06) L after 6 months of therapy (P = 0.028) (Figure). In the supine position, the FVC also changed significantly from 1.93 (1.03) L to 2.14 (1.11) L (P = 0.004). Five of 11 patients had diaphragm muscle weakness. They showed a similar increase in FVC.