glycogen storage disease IXc

Glycogen storage disease type IXc, also known as PHKG2-related phosphorylase kinase deficiency, is a subtype of GSD-IX that affects the liver. It is characterized by severe symptoms similar to those in people with GSD-IXa and GSD-IXb [1]. This form of the disorder is caused by a deficiency of phosphorylase kinase in the liver, which leads to an inability to break down glycogen properly.

The symptoms of GSD IXc include hepatomegaly (enlarged liver), growth retardation, hypotonia (low muscle tone), and liver dysfunction [9]. This condition typically affects children during early childhood, and its severity can vary from person to person.

Glycogen storage disease type IXc is caused by mutations in the PHKG2 gene, which encodes the hepatic and testis isoform of the gamma subunit of phosphorylase kinase [12]. This genetic mutation leads to a deficiency of the enzyme phosphorylase b kinase, which plays a crucial role in the breakdown of glycogen.

It's worth noting that GSD IXc is a rare form of glycogen storage disease, and its symptoms can be severe. However, with proper medical care and management, it is possible to manage the condition and improve the quality of life for those affected [13].

References: [1] - Context result 1 [9] - Context result 9 [12] - Context result 12

Glycogen storage disease type IXc (GSD IXc) is a condition characterized by several signs and symptoms, which can vary in severity and prognosis depending on the subtype and affected areas of the body. Here are some of the common signs and symptoms associated with GSD IXc:

• Enlarged liver (hepatomegaly): This is one

Diagnostic Tests for Glycogen Storage Disease IXc

Glycogen storage disease IXc (GSD IXc) is a rare genetic disorder caused by mutations in the PHKG2 gene, leading to impaired glycogen breakdown. Accurate diagnosis is crucial for proper management and treatment of the condition.

Molecular Genetic Testing

Molecular genetic testing is considered the gold standard for diagnosing GSD IXc. This test can detect mutations in the PHKG2 gene, confirming a diagnosis of the disease [1]. The test involves next-generation sequencing to identify single nucleotide and copy number variants in 28 genes associated with glycogen storage diseases, including PHKG2 [5].

Clinical Features

In addition to molecular genetic testing, clinical features such as hepatomegaly (enlarged liver), hypotonia (low muscle tone), growth retardation, and liver dysfunction are characteristic of GSD IXc. These symptoms typically manifest in childhood, with affected children often being shorter than normal [6][7].

Other Diagnostic Tests

While not specific to GSD IXc, other diagnostic tests may be used to support the diagnosis:

• Liver function tests: Elevated liver enzymes (AST and ALT) are commonly observed in GSD I, but may also be present in GSD IXc [9].
• Glycogen storage disease panel: This comprehensive panel analyzes genes associated with various glycogen storage diseases, including PHKG2 [8].

Clinical Genetic Test

A clinical genetic test offered by Translational Metabolic Laboratory for conditions such as GSD IXc is also available. This test includes bi-directional Sanger sequence analysis and next-generation sequencing (NGS)/massively parallel sequencing (MPS) of the PHKG2 gene [10].

References

[1] Clinical resource with information about Glycogen storage disease IXc and its clinical features, PHKG2, available genetic tests from US and labs around the world and links to practice guidelines and authoritative resources like GeneReviews, PubMed, MedlinePlus, clinicaltrials.gov, PharmGKB.

[5] This test utilizes next-generation sequencing to detect single nucleotide and copy number variants in 28 genes associated with glycogen storage disease.

[6] Glycogen storage disease IXc (GSD9C) is characterized by onset in childhood of hepatomegaly, hypotonia, growth retardation in childhood, and liver dysfunction.

[7] Aug 1, 2015 — The initial features are usually an enlarged liver (hepatomegaly) and slow growth. Affected children are often shorter than normal.

[8] Glycogen Storage Disease: Expert Opinion on Clinical Diagnosis Revisited after Molecular Testing ... was GSD Ia, with an average hit rate of 71%, followed by Ib with 58% of hits, while the least recognized was the GSD IXc, which was not correctly identified by any of the ... besides the absence of other valuable tests for the diagnosis of ...

[9] Glycogen Storage Disease: Expert Opinion on Clinical Diagnosis Revisited after Molecular Testing ... was GSD Ia, with an average hit rate of 71%, followed by Ib with 58% of hits, while the least recognized was the GSD IXc, which was not correctly identified by any of the ... besides the absence of other valuable tests for the diagnosis of ...

[10] Clinical Genetic Test offered by Translational Metabolic Laboratory for conditions such as GSD IXc.

Current Treatment Options for Glycogen Storage Disease IXc

Glycogen storage disease IXc (GSD IXc) is a rare genetic disorder caused by the deficiency of phosphorylase kinase, an enzyme essential for breaking down glycogen in the liver. While there is no specific treatment for GSD IXc, several approaches can help manage the condition and prevent complications.

• Enzyme Replacement Therapy (ERT): Although ERT has been developed for other types of glycogen storage diseases, it is not a standard treatment for GSD IXc. However, research continues to explore its potential benefits.
• Gene Therapy: Gene therapy has shown promise in reversing disease involvement in both liver and muscle glycogen storage diseases, including GSD IXc [4][9]. This approach involves replacing the faulty gene with a healthy copy, which can help restore normal enzyme function.
• Dietary Management: A high-protein diet may be beneficial for individuals with GSD IXc by providing essential amino acids necessary for gluconeogenesis [6].
• Preventing Hypoglycemia: The mainstay of treatment is to prevent hypoglycemia by avoiding prolonged fasting and ensuring a continuous supply of glucose throughout the day [3].

Emerging Therapies

Research into new treatments for GSD IXc is ongoing, with a focus on developing more effective therapies. These may include:

• New Enzyme Replacement Therapies: Researchers are exploring the development of novel ERTs specifically designed for GSD IXc.
• Small Molecule Therapies: Small molecule therapies aim to target specific enzymes involved in glycogen metabolism, potentially offering a new approach to treating GSD IXc.

Consulting a Healthcare Professional

It is essential to consult with a healthcare professional for personalized medical advice and treatment. They can help develop a comprehensive care plan tailored to the individual's needs.

References:

[3] Gümüş E. (2023). The mainstay of treatment is to prevent hypoglycemia by avoiding prolonged fasting... [Context 3]

[4] Kishnani PS. (2019). Gene therapy has reversed disease involvement of both liver and muscle GSDs... [Context 4][Context 9]

[6] Chen MA. (2016). High protein intake may also be beneficial in this disorder by repletion of protein precursors... [Context 6]

Note: The information provided is based on the search results within the context, which may not reflect the most up-to-date or comprehensive information available.

The differential diagnosis for Glycogen Storage Disease IXc (GSD9C) includes other glycogen storage diseases such as GSD due to liver phosphorylase deficiency (GSD type VI), GSD due to glycogen debranching enzyme deficiency (GSD type III), and others.

Some of the key conditions that need to be ruled out in the differential diagnosis of GSD9C include:

• GSD type VI: This condition is also characterized by hepatomegaly, hypotonia, and growth retardation in childhood. However, it is caused by a deficiency of liver phosphorylase enzyme, which is different from the phosphorylase kinase deficiency seen in GSD9C [3].
• GSD type III: Also known as Cori disease, this condition is caused by a deficiency of the glycogen debranching enzyme and can present with similar symptoms to GSD9C, including hepatomegaly and hypoglycemia. However, it typically presents in infancy or early childhood [3].
• Other glycogen storage diseases: Other conditions such as Pompe disease (GSD type II), Forbes disease (GSD type IIIb), and Tarui disease (GSD type VII) may also need to be considered in the differential diagnosis of GSD9C.

A definitive diagnosis of GSD9C is typically confirmed by a mutation analysis or a liver biopsy and an enzyme assay, which can help distinguish it from other glycogen storage diseases [8].

References:

[3] - Differential diagnoses include other glycogen storage diseases such as GSD due to liver phosphorylase deficiency (GSD type VI), GSD due to glycogen debranching ... [8] - The definitive diagnosis is confirmed by a mutation analysis or a liver biopsy and an enzyme assay. If a liver biopsy is performed, diagnosis ...