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INTRODUCTION

  1. At present, “Pompe disease” stands for the very broad clinical spectrum of glycogen storage disease type II (GSDII) including infantile, childhood, and adult variants. The name “acid maltase deficiency” (AMD) is also used. Pompe disease is one of more than 10 different GSDs (see Stomach Cancer: Glycogen Storage Diseases) and also one of nearly 60 different lysosomal disorders (see Defects of Electron Transfer Flavoprotein and Electron Transfer Flavoprotein-Ubiquinone Oxidoreductase: Glutaric Acidemia Type IIType III Hyperlipoproteinemia (Dysbetalipoproteinemia): The Role of Apolipoprotein E in Normal and Abnormal Lipoprotein Metabolism: Lysosomal Disorders [Part 16]). Pompe disease results from acid α-glucosidase (GAA) deficiency and is transmitted as an autosomal recessive trait.

  2. The clinical presentation of Pompe disease encompasses a range of phenotypes all of which include varying degrees of myopathy but differ with regard to age of onset, extent of organ involvement, and rate of progression. The most severe is the classic-infantile-onset disease, described by Pompe in 1932 and delineated prior to discovery of the deficiency of acid α-glucosidase (acid maltase), with cardiomyopathy, hypotonia, hepatomegaly, and death due to cardiorespiratory failure, usually before 1 year of age. Patients at the other end of the spectrum present in the third to seventh decade, usually with a slowly progressive proximal myopathy. Between these two extremes of the clinical spectrum there is a heterogeneous group, formerly termed childhood and juvenile variants, generally with onset after early infancy, a predominance of skeletal muscle involvement, usually without cardiac involvement, and a more slowly progressive course as compared with classic-infantile Pompe disease. Progressive proximal muscle weakness including major impairment of respiratory function dominates the picture. Death results usually from complications associated with respiratory failure.

  3. At the cellular level, the acid α-glucosidase deficiency results in intralysosomal accumulation of normally structured glycogen in numerous tissues. The accumulation is most marked in the skeletal muscles, the heart, and the liver of infants with classic-infantile Pompe disease. In children and adults with more slowly progressing forms of Pompe disease the heart and liver are virtually unaffected, and the intralysosomal accumulation of glycogen in muscle is of lesser magnitude. The pathology can vary in different muscles, and can be revealed by CT scans and MRI. As a result of muscle damage, patients across the clinical spectrum, but most so affected infants, usually have elevated blood plasma levels of creatine kinase (CK), aspartate aminotransferase (AST), and alanine aminotransferase (ALT). Glc4 is often present in the urine.

  4. The diagnosis “Pompe disease” is confirmed by the finding of a complete deficiency of acid α-glucosidase activity in all classic-infantile cases or a markedly reduced activity (usually <30% of average normal) in all other cases—in leukocytes, cultured skin fibroblasts, or muscle tissue. Blood spots can also be used for measuring the acid α-glucosidase activity and are most useful for screening purposes such as in newborn screening and in screening of patient populations with undiagnosed limb-girdle weakness or hyper CK-emia. The diagnosis “Pompe disease” can also be established ...

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