Expert Reviewed By: Dr. Brandon Colby MD
Glycogen storage disease II (GSD II), also known as Pompe disease, is a rare genetic disorder that affects the body's ability to break down glycogen, a complex sugar, into glucose. This leads to a buildup of glycogen in various organs, particularly the muscles and liver, causing progressive muscle weakness and organ damage. The adult form of GSD II is a late-onset variant that presents with milder symptoms and a slower progression compared to the infantile form. In this article, we will delve into understanding the adult form of GSD II, its diagnosis, and the role of genetic testing in managing this condition.
Understanding Adult-Onset Glycogen Storage Disease II
Adult-onset GSD II is caused by mutations in the GAA gene, which encodes an enzyme called acid alpha-glucosidase (GAA). This enzyme is responsible for breaking down glycogen into glucose. When the enzyme is deficient or absent, glycogen accumulates in cells, particularly in the muscles, leading to muscle weakness and respiratory problems (Targeted Disruption of the Acid α-Glucosidase Gene in Mice Causes an Illness with Critical Features of Both Infantile and Adult Human Glycogen Storage Disease Type II).
The adult form of GSD II is less severe than the infantile form, with symptoms often appearing in late childhood or adulthood. Common symptoms include muscle weakness, difficulty walking, and respiratory problems. In severe cases, the disease can lead to respiratory failure and death (GLYCOGEN STORAGE DISEASE TYPE II: A NARRATIVE LITERATURE REVIEW AND A CASE REPORT OF LATE-ONSET POMPE DISEASE IN A YOUNG WHITE CHILD).
Diagnosing Adult-Onset Glycogen Storage Disease II
Diagnosing adult-onset GSD II can be challenging due to its variable presentation and the rarity of the condition. A combination of clinical examination, biochemical tests, and genetic testing is often required to confirm the diagnosis. Muscle biopsies and enzyme activity assays can also be used to detect the presence of glycogen accumulation and reduced GAA enzyme activity (A Broad Characterization of Glycogen Storage Disease IV Patients: A Clinical, Genetic, and Histopathological Study).
The Role of Genetic Testing in Diagnosing GSD II
Genetic testing plays a crucial role in diagnosing GSD II, as it can identify the specific mutations in the GAA gene responsible for the disease. This information can help confirm the diagnosis, predict the severity of the disease, and guide treatment decisions. Genetic testing can also be used for carrier screening and prenatal diagnosis, allowing families to make informed decisions about family planning and the management of the condition (Targeted Disruption of the Acid α-Glucosidase Gene in Mice Causes an Illness with Critical Features of Both Infantile and Adult Human Glycogen Storage Disease Type II).
Using Genetic Testing for Prognosis and Treatment
Genetic testing can provide valuable information about the prognosis of adult-onset GSD II. Certain GAA gene mutations are associated with a milder disease course, while others may lead to a more severe presentation. Understanding the specific genetic mutations involved can help clinicians predict the likely progression of the disease and tailor treatment accordingly (GLYCOGEN STORAGE DISEASE TYPE II: A NARRATIVE LITERATURE REVIEW AND A CASE REPORT OF LATE-ONSET POMPE DISEASE IN A YOUNG WHITE CHILD).
Treatment for adult-onset GSD II often involves enzyme replacement therapy (ERT), which involves the administration of a recombinant human GAA enzyme. Genetic testing can help determine the potential effectiveness of ERT and identify patients who are likely to benefit from this treatment approach (Targeted Disruption of the Acid α-Glucosidase Gene in Mice Causes an Illness with Critical Features of Both Infantile and Adult Human Glycogen Storage Disease Type II).
Conclusion
Adult-onset GSD II is a rare and complex genetic disorder with a variable presentation. A combination of clinical examination, biochemical tests, and genetic testing is crucial for accurate diagnosis and management of the condition. Genetic testing plays a vital role in confirming the diagnosis, predicting disease severity, guiding treatment decisions, and providing valuable information for family planning. As our understanding of the genetic basis of GSD II continues to grow, so too will our ability to diagnose, treat, and manage this challenging condition.
About The Expert Reviewer
Dr. Brandon Colby MD is a US physician specializing in the personalized prevention of disease through the use of genomic technologies. He’s an expert in genetic testing, genetic analysis, and precision medicine. Dr. Colby is also the Founder of and the author of Outsmart Your Genes.
Dr. Colby holds an MD from the Mount Sinai School of Medicine, an MBA from Stanford University’s Graduate School of Business, and a degree in Genetics with Honors from the University of Michigan. He is an Affiliate Specialist of the American College of Medical Genetics and Genomics (ACMG), an Associate of the American College of Preventive Medicine (ACPM), and a member of the National Society of Genetic Counselors (NSGC)