Glycogen storage disease type VII

Glycogen storage disease type VII
ICD-10	E74.0
ICD-9	271.0
OMIM	232800
DiseasesDB	5314
MeSH	D006014

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Feham Tariq, MD [2]

Synonyms and keywords:

Overview

Tarui disease(Glycogen storage disease typeVII) is an autosomal recessive rare disease, clinically characterized by early exercise intolerance which manifests during childhood, muscle pain and myoglobinuria in 50% of the cases.

Historical Perspective

The historical perspective of the glycogen-storage disease type VII is as follows:

• In 1965, Tarui first described the phosphofructokinase (PFK) deficiency in 3 siblings with easy fatigability and exercise intolerance.
• The skeletal muscles of these patients had increased muscle glycogen content and high levels of hexose monophosphates.
• In 1967, Layer et al suggested autosomal recessive inheritence of the disease by detecting the disease in a 18 year old male.
• Also in 1967, Satoyoshi and Kowa postulated the role of a inhibitor in the development of disease.
• In 1980, Vora et al. studied a patient with myopathy and hemolysis which were assosciated with PFK deficiency.
• In 1983 Tani et al. studied two japenese with congenital nonspheroctyic hemolytic anemia and mild myopathy, having erthrocytic PFK deficiency.
• Assays for muscle PFK revealed almost undetectable activity, and erythrocyte PFK had about 50% normal activity.
• Tarui disease or glycogen-storage disease type VII has since been described in approximately 100 patients worldwide.

Classification

[Tarui disease] may be classified into five subtypes based on [classification method 1], [classification method 2], and [classification method 3]. [Disease name] may be classified into several subtypes based on [classification method 1], [classification method 2], and [classification method 3].

Pathophysiology

• Mutations in the PFKM gene cause Glycogen storage disease type VII.
• PFKM gene signals to make the PFKM subunit of an enzyme called phosphofructokinase, which plays a key role in the metabolism of the glycogen.
• The phosphofructokinase enzyme is made up of four subunits and is found in a variety of tissues.
• Different tissues have different combinations of these four subunits of phosphofructokinase enzyme.
• In skeletal muscles where the main source of energy is stored glycogen, the phosphofructokinase enzyme is solely composed of the PFKM subunits.
• To maintain normal blood sugar levels between meals or during exercise, glycogen is metabolized rapidly into the when energy is needed.
• Phosphofructokinase is involved in the above-mentioned chain of events that metabolizes glycogen to provide energy to muscle cells.
• The mutations of the PFKM gene results in non-functional or dysfunctional PFKM subunits.
• As a result, no functional phosphofructokinase is formed in skeletal muscles, and glycogen cannot be metabolized completely resulting in the accumulation of the partially metabolized glycogen in the skeletal muscle cells.
• If these skeletal muscles are put to a moderate strain such as exercise, cramping ensues as these muscles do not have access to glycogen as an energy source.
• In other tissues, other subunits that make up the phosphofructokinase enzyme likely compensate for the lack of PFKM subunits, and the enzyme is able to retain some function, this compensation may help explain why other tissues are not affected by PFKM gene mutations.

Genetics

• Glycogen storage disease type VII is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations.
• Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent.
• The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
• If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms.
• The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25% with each pregnancy.
• The risk to have a child who is a carrier like the parents is 50% with each pregnancy.
• The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%.
• Consanguineous marriages have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.

Causes

• Glycogen storage disease type VII is inherited as an autosomal recessive genetic disorder.
• GSD type VII is caused by mutation of phosphofructokinase gene in the muscle that results in a deficiency of the phosphofructokinase enzyme which converts fructose-6-phosphate to fructose-1,6-diphosphate.
• This is the rate-limiting step in the metabolism of the glucose into available energy, if the phosphofructokinase is deficient, energy is not available to muscles during heavy exercise and hence pain and cramps occur in the muscle.

Differentiating Tarui disease from Other Diseases

Number	Enzyme deficiency	Eponym	Incidence	Hypo- glycemia?	Hepato- megaly?	Hyperlip- idemia?	Muscle symptoms	Development/ prognosis	Other symptoms
GSD type I	glucose-6-phosphatase	von Gierke's disease	1 in 50,000- 100,000 births	Yes	Yes	Yes	None	Growth failure	Lactic acidosis, hyperuricemia
GSD type II	acid maltase	Pompe's disease	1 in 60,000- 140,000 births	No	Yes	No	Muscle weakness	*Death by age ~2 years (infantile variant)	heart failure
GSD type III	glycogen debrancher	Cori's disease or Forbes' disease	1 in 100,000 births	Yes	Yes	Yes	Myopathy
GSD type IV	glycogen branching enzyme	Andersen disease		No	Yes, also cirrhosis	No	None	Failure to thrive, death at age ~5 years
GSD type V	muscle glycogen phosphorylase	McArdle disease	1 in 100,000	No	No	No	Exercise-induced cramps, Rhabdomyolysis		Renal failure by myoglobinuria
GSD type VI	liver glycogen phosphorylase	Hers' disease	1 in 65,000- 85,000 births	Yes	Yes	No	None
GSD type VII	muscle phosphofructokinase	Tarui's disease		No	No	No	Exercise-induced muscle cramps and weakness	growth retardation	Haemolytic anaemia
GSD type IX	phosphorylase kinase, PHKA2	-		Yes	No	Yes	None	Delayed motor development, Growth retardation
GSD type XI	glucose transporter, GLUT2	Fanconi-Bickel syndrome		Yes	Yes	No	None
GSD type XII	Aldolase A	Red cell aldolase deficiency		?	?	?	Exercise intolerance, cramps
GSD type XIII	β-enolase	-		?	?	?	Exercise intolerance, cramps	Increasing intensity of myalgias over decades	Serum CK: Episodic elevations; Reduced with rest
GSD type 0	glycogen synthase	-		Yes	No	No	Occasional muscle cramping

Epidemiology and Demographics

The epidemiology and demographics of the Glycogen storage disease type VII are as follows:

• Glycogen storage disease type VII is thought to be a rare condition; more than 100 cases have been described in the scientific literature.
• The incidence of Glycogen storage disease type VII is 2.3 children per 100,000 births per year.
• Glycogen storage disease type VII commonly affects children, all patients of reported cases died by age 4 years.
• Glycogen storage disease type VII usually affects individuals of the individuals of Japanese and Ashkenazi Jewish descent.
• Glycogen storage disease type VII affects men and women equally.

Risk Factors

There are no established risk factors for [disease name].

OR

The most potent risk factor in the development of [disease name] is [risk factor 1]. Other risk factors include [risk factor 2], [risk factor 3], and [risk factor 4].

OR

Common risk factors in the development of [disease name] include [risk factor 1], [risk factor 2], [risk factor 3], and [risk factor 4].

OR

Common risk factors in the development of [disease name] may be occupational, environmental, genetic, and viral.

Screening

There is insufficient evidence to recommend routine screening for [disease/malignancy].

OR

According to the [guideline name], screening for [disease name] is not recommended.

OR

According to the [guideline name], screening for [disease name] by [test 1] is recommended every [duration] among patients with [condition 1], [condition 2], and [condition 3].

Natural History, Complications, and Prognosis

Common complications of Tarui disease include:

• Extertional rhabdomyolysis
• Renal failure
• Gout
• Hyperuricemia
• Erythrocyte hemolysis

Prognosis is generally excellent/good/poor, and the 1/5/10-year mortality/survival rate of patients with [disease name] is approximately [#]%.

Diagnosis

Diagnostic Criteria

The diagnosis of [disease name] is made when at least [number] of the following [number] diagnostic criteria are met: [criterion 1], [criterion 2], [criterion 3], and [criterion 4].

OR

The diagnosis of [disease name] is based on the [criteria name] criteria, which include [criterion 1], [criterion 2], and [criterion 3].

OR

The diagnosis of [disease name] is based on the [definition name] definition, which includes [criterion 1], [criterion 2], and [criterion 3].

OR

There are no established criteria for the diagnosis of [disease name].

History and Symptoms

The hallmark of tarui disease is muscle exercise intolerance.

The most common symptoms of [tarui disease] include:

• Muscle cramps
• Muscle tenderness
• Myoglobinuria

Less common symptoms of [tarui disease] include

• [symptom 1], [symptom 2], and [symptom 3].

Physical Examination

Patients with [disease name] usually appear [general appearance]. Physical examination of patients with [disease name] is usually remarkable for [finding 1], [finding 2], and [finding 3].

OR

Common physical examination findings of [disease name] include [finding 1], [finding 2], and [finding 3].

OR

The presence of [finding(s)] on physical examination is diagnostic of [disease name].

OR

The presence of [finding(s)] on physical examination is highly suggestive of [disease name].

Laboratory Findings

The following laboratory findings are seen in tarui disease:

More common findings

• Elevated serum creatine kinase
• Reduced red blood cell phosphofructokinase activity.
• Reticulocytosis
• Hyperurecemia

Less common findings

• Hemolytic anemia
• Mild hyperbilirubinemia

Laboratory findings
More common findings	Less common findings
Elevated serum creatine kinase Reduced red blood cell phosphofructokinase activity. Reticulocytosis Hyperurecemia	Hemolytic anemia Mild hyperbilirubinemia
Laboratory findings seen after exercise High concentrations of: Ammonia Inosine Hypoxanthine

Electrocardiogram

There are no ECG findings associated with [tarui disease].

X-ray

There are no x-ray findings associated with [disease name].

OR

An x-ray may be helpful in the diagnosis of [disease name]. Findings on an x-ray suggestive of/diagnostic of [disease name] include [finding 1], [finding 2], and [finding 3].

OR

There are no x-ray findings associated with [disease name]. However, an x-ray may be helpful in the diagnosis of complications of [disease name], which include [complication 1], [complication 2], and [complication 3].

Echocardiography or Ultrasound

There are no echocardiography/ultrasound findings associated with [disease name].

OR

Echocardiography/ultrasound may be helpful in the diagnosis of [disease name]. Findings on an echocardiography/ultrasound suggestive of/diagnostic of [disease name] include [finding 1], [finding 2], and [finding 3].

OR

There are no echocardiography/ultrasound findings associated with [disease name]. However, an echocardiography/ultrasound may be helpful in the diagnosis of complications of [disease name], which include [complication 1], [complication 2], and [complication 3].

CT scan

There are no CT scan findings associated with [disease name].

OR

[Location] CT scan may be helpful in the diagnosis of [disease name]. Findings on CT scan suggestive of/diagnostic of [disease name] include [finding 1], [finding 2], and [finding 3].

OR

There are no CT scan findings associated with [disease name]. However, a CT scan may be helpful in the diagnosis of complications of [disease name], which include [complication 1], [complication 2], and [complication 3].

MRI

There are no MRI findings associated with [disease name].

OR

[Location] MRI may be helpful in the diagnosis of [disease name]. Findings on MRI suggestive of/diagnostic of [disease name] include [finding 1], [finding 2], and [finding 3].

OR

There are no MRI findings associated with [disease name]. However, a MRI may be helpful in the diagnosis of complications of [disease name], which include [complication 1], [complication 2], and [complication 3].

Other Imaging Findings

There are no other imaging findings associated with [disease name].

OR

[Imaging modality] may be helpful in the diagnosis of [disease name]. Findings on an [imaging modality] suggestive of/diagnostic of [disease name] include [finding 1], [finding 2], and [finding 3].

Other Diagnostic Studies

There are no other diagnostic studies associated with [disease name].

OR

[Diagnostic study] may be helpful in the diagnosis of [disease name]. Findings suggestive of/diagnostic of [disease name] include [finding 1], [finding 2], and [finding 3].

OR

Other diagnostic studies for [disease name] include [diagnostic study 1], which demonstrates [finding 1], [finding 2], and [finding 3], and [diagnostic study 2], which demonstrates [finding 1], [finding 2], and [finding 3].

Treatment

Medical Therapy

There is no treatment for [disease name]; the mainstay of therapy is supportive care.

OR

Supportive therapy for [disease name] includes [therapy 1], [therapy 2], and [therapy 3].

OR

The majority of cases of [disease name] are self-limited and require only supportive care.

OR

[Disease name] is a medical emergency and requires prompt treatment.

OR

The mainstay of treatment for [disease name] is [therapy].

OR   The optimal therapy for [malignancy name] depends on the stage at diagnosis.

OR

[Therapy] is recommended for all patients who develop [disease name].

OR

Pharmacologic medical therapy is recommended among patients with [disease subclass 1], [disease subclass 2], and [disease subclass 3].

OR

Pharmacologic medical therapies for [disease name] include (either) [therapy 1], [therapy 2], and/or [therapy 3].

OR

Empiric therapy for [disease name] depends on [disease factor 1] and [disease factor 2].

OR

Patients with [disease subclass 1] are treated with [therapy 1], whereas patients with [disease subclass 2] are treated with [therapy 2].

Surgery

Surgical intervention is not recommended for the management of [disease name].

OR

Surgery is not the first-line treatment option for patients with [disease name]. Surgery is usually reserved for patients with either [indication 1], [indication 2], and [indication 3]

OR

The mainstay of treatment for [disease name] is medical therapy. Surgery is usually reserved for patients with either [indication 1], [indication 2], and/or [indication 3].

OR

The feasibility of surgery depends on the stage of [malignancy] at diagnosis.

OR

Surgery is the mainstay of treatment for [disease or malignancy].

Primary Prevention

There are no established measures for the primary prevention of [disease name].

OR

There are no available vaccines against [disease name].

OR

Effective measures for the primary prevention of [disease name] include [measure1], [measure2], and [measure3].

OR

[Vaccine name] vaccine is recommended for [patient population] to prevent [disease name]. Other primary prevention strategies include [strategy 1], [strategy 2], and [strategy 3].

Secondary Prevention

There are no established measures for the secondary prevention of [disease name].

OR

Effective measures for the secondary prevention of [disease name] include [strategy 1], [strategy 2], and [strategy 3].

References

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