Glycogen storage disease type III

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Anmol Pitliya, M.B.B.S. M.D.[2]

Glycogen storage disease type 3 (GSD 3) results due to deficiency of glycogen debrancher enzyme. Glycogen debrancher enzyme is present in the liver and muscle. Glycogen debrancher enzyme catalyzes the conversion of phosphorylase limit dextrin into glucose-6-phosphate during glycogenolysis. This defect hinders this conversion. The inability of glucose to leave cells leads to fasting hypoglycemia. of glycogenolysis leads to the accumulation of fat and glycogen deposition resulting in characteristic hepatomegaly. Hepatomegaly is more pronounced when the child is young and decreases as the age progresses. The hepatomegaly leads to protrusion of the abdomen. Myopathy is usually present and becomes more pronounced as age progress. AGL gene mutation is responsible for glycogen debrancher enzyme deficiency in GSD type 3 and is located on chromosome locus 1p21. GSD type 3 follows an autosomal recessive pattern. AGL gene mutation responsible for the glycogen debranching enzyme (GDE) deficiency is located on chromosome 1p21. The incidence of glycogen storage disease type 3 (GSD 3) is approximately 1 per 100,000 individuals in the United States of America. The most potent risk factor in the development of glycogen storage disease type 3 is a sibling with glycogen storage disease type 3. If left untreated, patients with glycogen storage disease type 3 grow slowly and puberty is delayed. The myopathy of glycogen storage disease type 3 typically develop in the third to fourth decades of life. It manifests as muscle weakness which is slow and progressive and usually involves large proximal muscle of the shoulder and hips. Common complications of glycogen storage disease type 3 include left ventricular hypertrophy, myopathy, cardiomyopathy, hepatic adenoma with transformation into hepatocellular carcinoma, cirrhosis and hyperlipidemia. Prognosis is generally good after treatment. The presence of liver disease is associated with a particularly poor prognosis among patients with glycogen storage disease type 3. The hallmark of glycogen storage disease type 3 is hepatomegaly. The most common symptoms of glycogen storage disease include abdominal protuberance and muscle weakness. Physical examination of patients with glycogen storage disease type 3 is usually remarkable for protruding abdomen due to marked hepatomegaly and proximal muscle weakness. Laboratory findings consistent with the diagnosis of glycogen storage disease type 3 include ketotic hypoglycemia, increased creatine kinase, hyperlipidemia, and elevated liver transaminases. Glycogen storage disease type 3 is diagnosed by identification of proband by molecular genetic testing. Molecular genetic testing shows biallelic pathogenic variants in AGL for patients with GSD type 3. The medical therapy of glycogen storage disease type 3 is directed towards management of hypoglycemia. However, hypoglycemic episodes are less marked in glycogen storage disease type 3 than glycogen storage disease type 1. A high protein diet is recommended, especially for children with growth failure and myopathy. A metabolic dietician should be consulted once a case of GSD type 3 is diagnosed. Preferred treatment is use of cornstarch. Liver transplantation is indicated for patients developing histologiocal evidence of cirrhosis. Effective measures for primary prevention of glycogen storage disease type 3 include genetic counseling, prenatal diagnosis, and screening.

In 1928, van Creveld first described a case of a 7-year-old boy presented with a marked hepatomegaly, obesity and small genitalia. In 1956, B Illingworth, GT Cori, and CF Cori confirmed that glycogen storage disease type 3 is due to deficiency of amylo-1, 6-glucosidase (glycogen debranching enzyme).

Glycogen storage disease type III may be classified according to the site and/or types of enzyme-deficient into 4 subtypes including glycogen storage disease type 3a, type 3b, type 3c, and type 3d.

Glycogen storage disease type 3 (GSD 3) results due to deficiency of glycogen debrancher enzyme. Glycogen debrancher enzyme is present in the liver and muscle. Glycogen debrancher enzyme catalyzes the conversion of phosphorylase limit dextrin into glucose-6-phosphate during glycogenolysis. This defect hinders this conversion. The inability of glucose to leave cells leads to fasting hypoglycemia. Impairment of glycogenolysis leads to the accumulation of fat and glycogen deposition resulting in characteristic hepatomegaly. Hepatomegaly is more pronounced when the child is young and decreases as the age progresses. The hepatomegaly leads to protrusion of the abdomen. Myopathy is usually present and becomes more pronounced as age progress. AGL gene mutation is responsible for glycogen debrancher enzyme deficiency in GSD type 3 and is located on chromosome locus 1p21. GSD type 3 follows an autosomal recessive pattern.

Glycogen storage disease type 3 is an autosomal recessive disorder. Glycogen storage disease type 3 is caused by the deficiency of the glycogen debranching enzyme (GDE). AGL gene mutation responsible for the glycogen debranching enzyme (GDE) deficiency is located on chromosome 1p21.

The incidence of glycogen storage disease type 3 (GSD 3) is approximately 1 per 100,000 individuals in the United States of America. 24% Cases of glycogen storage disease are of GSD type 3. In Israel, the prevalence of glycogen storage disease type 3 is approximately 18.5 per 100,000 individuals among North African Jews. Glycogen storage disease type 1 is usually first diagnosed in childhood. Glycogen storage disease type III affects men and women equally. In Faroese population of the Faroe Islands the prevalence of glycogen storage disease type 3a is approximately 32.25 per 100,000 individuals. This highest prevalence of glycogen storage disease type 3a worldwide is due to the founder effect.

The most potent risk factor in the development of glycogen storage disease type 3 is a sibling with glycogen storage disease type 3.

Glycogen storage disease type 3 is an autosomal recessive disease so carrier screening of at-risk relatives may be done. Screening requires prior identification of AGL pathogenic variants in the family.

If left untreated, patients with glycogen storage disease type 3 grow slowly and puberty is delayed. The myopathy of glycogen storage disease type 3 typically develop in the third to fourth decades of life. It manifests as muscle weakness which is slow and progressive and usually involves large proximal muscle of the shoulder and hips. Common complications of glycogen storage disease type 3 include left ventricular hypertrophy, myopathy, cardiomyopathy, hepatic adenoma with transformation into hepatocellular carcinoma, cirrhosis and hyperlipidemia. Prognosis is generally good after treatment. The presence of liver disease is associated with a particularly poor prognosis among patients with glycogen storage disease type 3.

Glycogen storage disease type 3 is diagnosed by identification of proband by molecular genetic testing. Molecular genetic testing shows biallelic pathogenic variants in AGL for patients with GSD type 3.

The hallmark of glycogen storage disease type 3 is hepatomegaly. The most common symptoms of glycogen storage disease include abdominal protuberance and muscle weakness.

Physical examination of patients with glycogen storage disease type 3 is usually remarkable for protruding abdomen due to marked hepatomegaly and proximal muscle weakness.

Laboratory findings consistent with the diagnosis of glycogen storage disease type 3 include ketotic hypoglycemia, increased creatine kinase, hyperlipidemia, and elevated liver transaminases.

An ECG may be helpful in the diagnosis of cardiac abnormalities associated with glycogen storage disease type 3. Findings on an ECG suggestive of cardiac abnormalities associated with glycogen storage disease type 3 include left ventricular hypertrophy.

There are no x-ray findings associated with glycogen storage disease type 3.

Echocardiography may be helpful in the detection of cardiomyopathy due to glycogen storage disease type 3. Findings on an echocardiography suggestive of cardiomyopathy due to echocardiography include elevated left ventricular mass and thickness. Ultrasound may be helpful in the diagnosis of glycogen storage disease type 3. Findings on an ultrasound suggestive of glycogen storage disease type 3 include hepatomegaly and increased hepatic echogenicity. Abdominal ultrasound should be performed at baseline and every 12-24 months to detect evidence of cirrhosis, hepatic adenoma, and hepatocellular carcinoma.

Abdominal computed tomography or magnetic resonance imaging with contrast is performed to screen for evidence of liver cirrhosis, hepatic adenoma, and hepatocellular carcinoma.

Abdominal magnetic resonance imaging or computed tomography with contrast is performed to screen for evidence of liver cirrhosis, hepatic adenoma, and hepatocellular carcinoma.

Dual energy X-ray absorptiometry (DXA) may be helpful in the diagnosis of low bone mineral density (BMD) in patients with glycogen storage disease type 3.

Other studies used for diagnosis of glycogen storage disease type 3 include identification of proband by either molecular genetic testing or enzyme activity assay. Molecular genetic testing shows biallelic pathogenic variants in AGL gene for patients with GSD type 3. Enzyme activity assay is performed for glycogen debranching enzyme activity. Molecular genetic testing is the diagnostic study of choice for glycogen storage disease type 3.

The medical therapy of glycogen storage disease type 3 is directed towards management of hypoglycemia. However, hypoglycemic episodes are less marked in glycogen storage disease type 3 than glycogen storage disease type 1. A high protein diet is recommended, especially for children with growth failure and myopathy. A metabolic dietician should be consulted once a case of GSD type 3 is diagnosed. Preferred treatment is use of cornstarch. Careful monitoring of blood glucose is needed during illness, if diet or schedule is changed, start of exercise routine, and randomly to detect asymptomatic hypoglycemia.

Liver transplantation is indicated for patients developing histologiocal evidence of cirrhosis. There is resolution of metabolic derangements after liver transplantation in patients with glycogen storage disease type 3 (GSD 3). As hepatic abnormalities in GSD 3 are due to single-gene and cell-autonomous defect, the recurrence of primary liver disease in the transplanted allograft in not possible. However, skeletal manifestations or cardiac manifestations doesnot correct even after liver transplantation.

Effective measures for primary prevention of glycogen storage disease type 3 include genetic counseling, prenatal diagnosis, and screening.

Effective measures for the secondary prevention of glycogen storage disease type 3 include blood glucose monitoring, prevent overtreatment, general medical care recommendations, gastrointestinal/nutritional recommendations, cardiology recommendations, physical therapy, surgery/anesthesia recommendations, and gynecological/obstetrical recommendations.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Anmol Pitliya, M.B.B.S. M.D.[2]

In 1928, van Creveld first described a case of a 7-year-old boy presented with a marked hepatomegaly, obesity and small genitalia. In 1956, B Illingworth, GT Cori, and CF Cori confirmed that glycogen storage disease type 3 is due to deficiency of amylo-1, 6-glucosidase (glycogen debranching enzyme).

• In 1928, van Creveld first described a case of a 7-year-old boy presented with a marked hepatomegaly, obesity and small genitalia. He termed it as “an unusual disturbance of carbohydrate metabolism in childhood”. This was later proved to be glycogen storage disease type 3. ^[1]
• In 1952, Barbara Illingworth and Gerty Cori predicted deficiency of glycogen debranching enzyme in follow-up patients of Gilbert Forbes. These patients had excessive storage of abnormal glycogen in liver and muscle.^[2]
• In 1956, B Illingworth, GT Cori, and CF Cori confirmed that glycogen storage disease type 3 is due to deficiency of amylo-1, 6-glucosidase (glycogen debranching enzyme).^[3]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Anmol Pitliya, M.B.B.S. M.D.[2]

Glycogen storage disease type III may be classified according to the site and/or types of enzyme-deficient into 4 sub-types including glycogen storage disease type 3a, type 3b, type 3c, and type 3d.

Glycogen storage disease type III may be classified according to the site and/or types of enzyme-deficient into 4 subtypes:^[1][2][3]

Type of GDS 3	Type of defect	Molecular mechanism
Glycogen storage disease type 3a	Enzyme deficiency in both liver and muscle	Both glycogen debranching enzymes (GDE) deficiency
Glycogen storage disease type 3b	Enzyme deficient in liver only	Both glycogen debranching enzymes (GDE) deficiency
Glycogen storage disease type 3c	Isolate enzyme deficiency	Isolated glucosidase deficiency with retention of transferase activity
Glycogen storage disease type 3d	Isolate enzyme deficiency	Isolated transferase deficiency with retention of glucosidase activity

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Anmol Pitliya, M.B.B.S. M.D.[2]

Glycogen storage disease type 3 (GSD 3) results due to deficiency of glycogen debrancher enzyme. Glycogen debrancher enzyme is present in the liver and muscle. Glycogen debrancher enzyme catalyzes the conversion of phosphorylase limit dextrin into glucose-6-phosphate during glycogenolysis. This defect hinders this conversion. The inability of glucose to leave cells leads to fasting hypoglycemia. Impairment of glycogenolysis leads to the accumulation of fat and glycogen deposition resulting in characteristic hepatomegaly. Hepatomegaly is more pronounced when the child is young and decreases as the age progresses. The hepatomegaly leads to protrusion of the abdomen. Myopathy is usually present and becomes more pronounced as age progress. AGL gene mutation is responsible for glycogen debrancher enzyme deficiency in GSD type 3 and is located on chromosome locus 1p21. GSD type 3 follows an autosomal recessive pattern.

• Glycogen storage disease type 3 (GSD 3) results due to deficiency of glycogen debrancher enzyme.
• GSD type 3a is due to the deficiency of enzyme glycogen debrancher enzyme in both liver and muscle.
• GSD type 3b is due to the deficiency of enzyme glycogen debrancher enzyme in liver only.

• Glycogen debrancher enzyme is present in the liver and muscle.^[1][2]
• Glycogen debrancher enzyme catalyzes the conversion of phosphorylase limit dextrin into glucose-6-phosphate during glycogenolysis.
• Absence of glycogen debrancher enzyme hinders glycogenolysis.
• This leads to accumulation of limit dextrin in organs including liver and muscle.
• The inability of glucose to leave cells leads to fasting hypoglycemia.
• This also results in the development of various secondary metabolic and biochemical abnormalities.

• Impairment of glycogenolysis leads to the accumulation of fat and glycogen deposition, resulting in characteristic hepatomegaly.
• Hepatomegaly is more pronounced when the child is young and decreases as the age progresses. The hepatomegaly leads to protrusion of the abdomen.
• Patients with GSD type 2 may develop hepatic lesions including:^{[3][4][5][6][7]}
  • Hepatocellular adenoma
  • Hepatocellular carcinoma
  • Cirrhosis
  • End-stage liver disease

• The following different phenotypes of myopathy are described in glycogen storage disease type 3:^[8]
  • Adult onset distal myopathy
  • Subacute myopathy of the respiratory muscles
  • Severe generalized myopathy
  • Minimal variant myopathy
• Exercise intolerance is usually not present.

• GSD type 3 follows an autosomal recessive pattern.
• AGL gene mutation is responsible for glycogen debrancher enzyme deficiency in GSD type 3 and is located on chromosome locus 1p21.^[9][10]

• Conditions associated with glycogen storage disease type 3 include:^[11]
  • Cardiomyopathy
  • Hyperlipidemia
  • Myopathy

• On gross pathology analysis, the features of glycogen storage disease type 1 include hepatomegaly. Hepatomegaly decreases as age increases.^[12]

On microscopic histopathological analysis, the features of glycogen storage disease type 1 include:

• Liver^[12]
  • Early disease
    • Distension of hepatocytes by glycogen
    • Periportal septal fibrosis
  • Late disease
    • Steatosis
    • Hepatocyte ballooning
    • Eventually centrilobular and portal-based fibrosis
• Muscles
  • Accumulation of glycogen between intact myofibrils and in subsarcolemmal position^[13]
• Heart
  • Endomyocardial biopsy specimen shows:^[14]
    • Glycogen deposition in myocytes
    • Myocyte disarray is not present

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Anmol Pitliya, M.B.B.S. M.D.[2]

Glycogen storage disease type 3 is an autosomal recessive disorder. Glycogen storage disease type 3 is caused by the deficiency of the glycogen debranching enzyme (GDE). AGL gene mutation responsible for the glycogen debranching enzyme (GDE) deficiency is located on chromosome 1p21.

• Glycogen storage disease type 3 is an autosomal recessive disorder.
• Glycogen storage disease type 3 is caused by the deficiency of the glycogen debranching enzyme (GDE). AGL gene mutation responsible for the glycogen debranching enzyme (GDE) deficiency is located on chromosome 1p21.^[1]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:

[Disease name] must be differentiated from other diseases that cause [clinical feature 1], [clinical feature 2], and [clinical feature 3], such as [differential dx1], [differential dx2], and [differential dx3].

OR

[Disease name] must be differentiated from [[differential dx1], [differential dx2], and [differential dx3].

• [Disease name] must be differentiated from other diseases that cause [clinical feature 1], [clinical feature 2], and [clinical feature 3], such as [differential dx1], [differential dx2], and [differential dx3].
• [Disease name] must be differentiated from [[differential dx1], [differential dx2], and [differential dx3].

• As [disease name] manifests in a variety of clinical forms, differentiation must be established in accordance with the particular subtype. [Subtype name 1] must be differentiated from other diseases that cause [clinical feature 1], such as [differential dx1] and [differential dx2]. In contrast, [subtype name 2] must be differentiated from other diseases that cause [clinical feature 2], such as [differential dx3] and [differential dx4].

Diseases	History and Symptoms				Physical Examination				Laboratory Findings				Other Findings
	Finding 1	Finding 2	Finding 3	Finding 4	Physical Finding 1	Physical Finding 2	Physical Finding 3	Physical Finding 4	Lab Test 1	Lab Test 2	Lab Test 3	Lab Test 4
Differential Diagnosis 1			+
Differential Diagnosis 2	↑			–
Differential Diagnosis 3		↓
Differential Diagnosis 4
Differential Diagnosis 5

Differential Diagnosis	Similar Features	Differentiating Features
Differential 1	On [physical exam; history; diagnostic test; imaging], [Differential 1] {has; demonstrates} [feature 1], [feature 2], [feature 3] also observed in [disease name].	On [physical exam; history; diagnostic test; imaging], [Differential 1] {has; demonstrates} [feature 1], [feature 2], [feature 3] that distinguish it from [disease name].
Differential 2	On [physical exam; history; diagnostic test; imaging], [Differential 1] {has; demonstrates} [feature 1], [feature 2], [feature 3] also observed in [disease name].	On [physical exam; history; diagnostic test; imaging], [Differential 1] {has; demonstrates} [feature 1], [feature 2], [feature 3] that distinguish it from [disease name].
Differential 3	On [physical exam; history; diagnostic test; imaging], [Differential 1] {has; demonstrates} [feature 1], [feature 2], [feature 3] also observed in [disease name].	On [physical exam; history; diagnostic test; imaging], [Differential 1] {has; demonstrates} [feature 1], [feature 2], [feature 3] that distinguish it from [disease name].
Differential 4	On [physical exam; history; diagnostic test; imaging], [Differential 1] {has; demonstrates} [feature 1], [feature 2], [feature 3] also observed in [disease name].	On [physical exam; history; diagnostic test; imaging], [Differential 1] {has; demonstrates} [feature 1], [feature 2], [feature 3] that distinguish it from [disease name].
Differential 5	On [physical exam; history; diagnostic test; imaging], [Differential 1] {has; demonstrates} [feature 1], [feature 2], [feature 3] also observed in [disease name].	On [physical exam; history; diagnostic test; imaging], [Differential 1] {has; demonstrates} [feature 1], [feature 2], [feature 3] that distinguish it from [disease name].

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Anmol Pitliya, M.B.B.S. M.D.[2]

The incidence of glycogen storage disease type 3 (GSD 3) is approximately 1 per 100,000 individuals in the United States of America. 24% Cases of glycogen storage disease are of GSD type 3. In Israel, the prevalence of glycogen storage disease type 3 is approximately 18.5 per 100,000 individuals among North African Jews. Glycogen storage disease type 1 is usually first diagnosed in childhood. Glycogen storage disease type III affects men and women equally. In Faroese population of the Faroe Islands the prevalence of glycogen storage disease type 3a is approximately 32.25 per 100,000 individuals. This highest prevalence of glycogen storage disease type 3a worldwide is due to the founder effect.

• The incidence of glycogen storage disease type 3 (GSD 3) is approximately 1 per 100,000 individuals in the United States of America.^[1]
• 24% cases of glycogen storage disease are of GSD type 3.^[2]
• 80% cases of GSD type 3 are of GSD type 3a.
• 15% cases of GSD type 3 are of GSD type 3b.
• GSD type 3c and GSD type 3d are rare.

• In Israel, the prevalence of glycogen storage disease type 3 is approximately 18.5 per 100,000 individuals among North African Jews.^[1]
• In Israel, the carrier prevalence of glycogen storage disease type 3 is approximately 2857 per 100,000 individuals among North African Jews.^[1]
• In Faroese population of the Faroe Islands the calculated prevalence of glycogen storage disease type 3 is approximately 28 per 100,000 individuals.^[3]
• In Faroese population of the Faroe Islands the prevalence of glycogen storage disease type 3a is approximately 32.25 per 100,000 individuals. This highest prevalence of glycogen storage disease type 3a worldwide is due to the founder effect.^[3]

• Glycogen storage disease type 3 is usually first diagnosed in childhood.^[4]

• Glycogen storage disease type III usually affects individuals of the Faroese population of the Faroe Islands.^[3]

• Glycogen storage disease type III affects men and women equally. ^[5]

• In Faroese population of the Faroe Islands the calculated prevalence of glycogen storage disease type 3 is approximately 28 per 100,000 individuals.^[3]
• In Faroese population of the Faroe Islands the prevalence of glycogen storage disease type 3a is approximately 32.25 per 100,000 individuals. This highest prevalence of glycogen storage disease type 3a worldwide is due to the founder effect.^[3]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Anmol Pitliya, M.B.B.S. M.D.[2]

The most potent risk factor in the development of glycogen storage disease type 3 is a sibling with glycogen storage disease type 3.

The most potent risk factor in the development of glycogen storage disease type 3 is a sibling with glycogen storage disease type 3.^[1]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Anmol Pitliya, M.B.B.S. M.D.[2]

Glycogen storage disease type 3 is an autosomal recessive disease so carrier screening of at-risk relatives may be done. Screening requires prior identification of AGL pathogenic variants in the family.

• Glycogen storage disease type 3 is an autosomal recessive disease.^[1]
• Carrier screening of at-risk relatives may be done.
• Screening requires prior identification of AGL pathogenic variants in the family.

Template:WH Template:WS

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Anmol Pitliya, M.B.B.S. M.D.[2]

If left untreated, patients with glycogen storage disease type 3 grow slowly and puberty is delayed. The myopathy of glycogen storage disease type 3 typically develop in the third to fourth decades of life. It manifests as muscle weakness which is slow and progressive and usually involves large proximal muscle of the shoulder and hips. Common complications of glycogen storage disease type 3 include left ventricular hypertrophy, myopathy, cardiomyopathy, hepatic adenoma with transformation into hepatocellular carcinoma, cirrhosis and hyperlipidemia. Prognosis is generally good after treatment. The presence of liver disease is associated with a particularly poor prognosis among patients with glycogen storage disease type 3.

• If left untreated, patients with glycogen storage disease type 3 grow slowly and puberty is delayed.^[1]
• The myopathy of glycogen storage disease type 3 typically develop in the third to fourth decades of life. It manifests as muscle weakness which is slow and progressive and usually involves large proximal muscle of the shoulder and hips.
• Accumulation of limit dextrin in cardiac muscles causes cardiomyopathy with echocardiographic findings similar to idiopathic hypertrophic cardiomyopathy.
• Hepatomegaly improves as the age progresses.

• Common complications of glycogen storage disease type III include:^{[2][3][4][5][6]}
  • Left ventricular hypertrophy
  • Hepatic adenoma with transformation into hepatocellular carcinoma
  • Cirrhosis
  • Myopathy
  • Cardiomyopathy
  • Hyperlipidemia
    • Hypercholesterolemia
    • Hypertriglyceridemia

• Prognosis is generally good after treatment.^[7]
• The presence of liver disease is associated with a particularly poor prognosis among patients with glycogen storage disease type 3.

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