Diurnal variability of glucose tetrasaccharide (Glc4) excretion in patients with glycogen storage disease type III

Improved Enzyme Replacement Therapy with Cipaglucosidase Alfa/Miglustat in Infantile Pompe Disease

Pompe disease is a lysosomal storage disorder with impaired glycogen degradation caused by a deficiency of the enzyme acid α-glucosidase (GAA). Children with the severe infantile form do not survive beyond the first year of life without treatment. Since 2006, enzyme replacement therapy (ERT) with Alglucosidase alfa (Myozyme) has been available, which is a recombinant human GAA (rhGAA). Myozyme therapy has prolonged the life span of affected patients, but many patients showed a continuing, albeit slower, disease progression. A new generation of rhGAA, Cipaglucosidase alfa (Amicus) has a higher content of mannose-6-phosphate residues, which are necessary for efficient cellular uptake and lysosomal targeting. Cipaglucosidase alfa is co-administered with an enzyme stabilizer, Miglustat, which also optimizes the pharmacological properties. In mouse models, the superiority of Cipaglucosidase alfa/Miglustat compared to the previous standard therapy could be determined. Here, we report the disease course of a patient with severe infantile M. Pompe, who showed serious progression even with high-dose standard of care ERT. Changing the therapy to Cipaglucosidase alfa/Miglustat improved respiratory failure, cardiomyopathy, and motor functions significantly. The patient could be weaned from respiratory support and oxygen supplementation. Cardiac function was normalized. Most impressively, the patient, who had lost nearly all motor skills, acquired head control, learned to speak, and could move his wheelchair by himself. Overall, the patient's clinical situation has improved dramatically with the new ERT.

A retrospective longitudinal study and comprehensive review of adult patients with glycogen storage disease type III

INTRODUCTION

A deficiency of glycogen debrancher enzyme in patients with glycogen storage disease type III (GSD III) manifests with hepatic, cardiac, and muscle involvement in the most common subtype (type a), or with only hepatic involvement in patients with GSD IIIb.

OBJECTIVE AND METHODS

To describe longitudinal biochemical, radiological, muscle strength and ambulation, liver histopathological findings, and clinical outcomes in adults (≥18 years) with glycogen storage disease type III, by a retrospective review of medical records.

RESULTS

Twenty-one adults with GSD IIIa (14 F & 7 M) and four with GSD IIIb (1 F & 3 M) were included in this natural history study. At the most recent visit, the median (range) age and follow-up time were 36 (19-68) and 16 years (0-41), respectively. For the entire cohort: 40% had documented hypoglycemic episodes in adulthood; hepatomegaly and cirrhosis were the most common radiological findings; and 28% developed decompensated liver disease and portal hypertension, the latter being more prevalent in older patients. In the GSD IIIa group, muscle weakness was a major feature, noted in 89% of the GSD IIIa cohort, a third of whom depended on a wheelchair or an assistive walking device. Older individuals tended to show more severe muscle weakness and mobility limitations, compared with younger adults. Asymptomatic left ventricular hypertrophy (LVH) was the most common cardiac manifestation, present in 43%. Symptomatic cardiomyopathy and reduced ejection fraction was evident in 10%. Finally, a urinary biomarker of glycogen storage (Glc4) was significantly associated with AST, ALT and CK.

CONCLUSION

GSD III is a multisystem disorder in which a multidisciplinary approach with regular clinical, biochemical, radiological and functional (physical therapy assessment) follow-up is required. Despite dietary modification, hepatic and myopathic disease progression is evident in adults, with muscle weakness as the major cause of morbidity. Consequently, definitive therapies that address the underlying cause of the disease to correct both liver and muscle are needed.