The late-onset form of Pompe disease

A case report is presented of a female patient with adult-onset Pompe disease (GSD II). The patient was diagnosed when 21 years old and is now being successfully treated with replacement therapy. The author provides an overview of the current knowledge on the aetiopathogenesis, classification, diagnostic procedures, and treatment options of this congenital disease. Pompe disease (glycogen storage disease type 2, deficiency of alpha-glucosidase enzyme) is a hereditary autosomal recessive metabolic disorder caused by the deficiency of the lysosomal acid alpha-glucosidase enzyme leading to the accumulation/storing of lysosome glycogen in cells and tissues followed by their dysfunction, especially in the heart and skeletal muscles. The structural gene of alpha-glucosidase has been found on chromosome 17q23. The pathogenesis is variable and dependent on the remaining activity of the alpha-glucosidase. If the cleaving enzyme is almost or completely non-functional, the infantile or classic onset form is usually developed. Symptoms usually develop in the first months of life in the form of general ill-development and muscle weakness, which affects even respiratory muscles, liver and heart. The disease progresses quickly and the death mostly occurs within the first year of age due to cardio-respiratory failure. The late-onset form is characterized by the less progressive phenotype during the emergence of serious mutation of one allele and less severe mutation on the other. The manifestation of this form of the disease occurs from the first decade of life to the sixth decade. Skeletal and respiratory muscles and diaphragm are first to be affected by this form of the disease. The progression is slow and the myocardium usually unaffected. The diagnosis of Pompe disease takes place in two levels. The first level is the screening testing of the dried blood spot (DBS). The diagnosis is then confirmed by determining the activity of acid alpha-glucosidase in white cells. The breakthrough in the field of treatment was the implementation of enzyme replacement therapy (ERT). The drug Myozyme (recombinant human enzyme) is available now. There is a case report of a woman with gradual symptomatic progression from childhood to adulthood in the article. The slowing of the progression and medical problems due to the substitution therapy is also shown.

Keywords: Pompe disease, alpha-glucosidase deficiency, lysosomal storage diseases, limb-girdle muscular weakness, enzyme replacement therapy.