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Adult-onset acid maltase deficiency: a postmortem study.
Muscle & Nerve
|January 1, 1978
Summary
Adult-onset acid maltase deficiency (AMD) selectively affects skeletal muscle due to the lowest residual enzyme activity. This postmortem study reveals vacuolar myopathy linked to significantly reduced acid maltase levels.
Area of Science:
- Biochemistry
- Neuromuscular Disorders
- Enzymology
Background:
- Adult-onset acid maltase deficiency (AMD), a lysosomal glycogen storage disease, is characterized by progressive muscle weakness.
- The precise mechanisms underlying tissue-specific pathology in late-onset AMD remain incompletely understood.
Observation:
- A postmortem examination of a patient with adult-onset AMD revealed morphological abnormalities primarily in skeletal muscle, presenting as vacuolar myopathy.
- Enzyme assays demonstrated significantly reduced acid maltase activity across multiple tissues, including muscle, liver, brain, and heart.
Findings:
- Residual acid maltase activity was approximately 6% of normal in muscle, liver, and brain, and 3% in the heart.
- Kinetic and inhibition studies confirmed the residual activity was authentic acid maltase.
- While neutral maltase activity was largely unaffected in muscle and liver, it was decreased in brain and heart.
Implications:
- The lowest absolute residual acid maltase activity in skeletal muscle may explain the selective and prominent involvement of this tissue in late-onset AMD.
- Understanding these enzyme kinetics provides insights into the pathogenesis of AMD and potential therapeutic targets.
- This study highlights the importance of quantitative enzyme analysis in correlating biochemical deficits with clinical manifestations in genetic disorders.