Glycogen storage disease type 2 (GSD2, MIM #232300) is an autosomal recessive inborn error of glycogen metabolism caused by deficiency of acid alpha-glucosidase (GAA), which is required for the degradation of lysosomal glycogen. GSD2 is characterised by lysosomal accumulation of glycogen in many body tissues as opposed to the exclusive cytoplasmic accumulation of glycogen that occurs in most other glycogen storage disorders. Clinical presentation varies from a rapidly fatal infantile disease to a slowly progressive late-onset myopathy frequently associated with respiratory insufficiency. Generally there is a correlation between the severity of the disorder and the amount of residual GAA activity. Incidence varies by ethnicity; in the Caucasian population the frequency of infantile disease is between 1:100,000 and 1:200,000 and late-onset disease possibly as high as 1:60,000. The GAA gene consists of 20 exons (exon 1 non-coding) and family specific mutations are found throughout the gene. Ethnic specific mutations are recognised and information regarding ethnic origin is a useful indicator. A mild splicing mutation in intron 1 (c.-32-13T>G) in combination with a more severe mutation is commonly associated with the late-onset phenotype in Caucasians.
Also known as
Pompe disease, acid maltase deficiency, GAA deficiency, acid alpha-glucosidase deficiency
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Clinically affected patients should have their diagnosis confirmed by enzyme analysis; this should be arranged either locally or with the Enzyme Unit, Chemical Pathology, Great Ormond Street Hospital. Biochemically confirmed patients can be referred for mutation analysis. If the necessary patient samples are unavailable genetic testing can be undertaken in the parents of the affected child. Information regarding ethnic origin is useful.
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Great Ormond Street Hospital NE Thames Regional Genetics Service Laboratories
Great Ormond Street Hospital for Children
37 Queen Square
1ml EDTA neonates, 5ml EDTA adults
Disease / group
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Prenatals must be arranged in advance, through a Clinical Genetics department if possible. Amniotic fluid or CV samples should be sent to Cytogenetics for dissecting and culturing, with instructions to forward the sample to the Regional Molecular Genetics laboratory for analysis