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Glycogen storage disease type II

Glycogen storage disease type II (also called Pompe disease or infantile acid maltase deficiency) is a rare genetic disorder caused by a deficiency in the enzyme acid alpha-glucosidase (GAA), which is needed to break down glycogen, a stored form of sugar used for energy. It is the only glycogen storage disease with a defect in lysosomal metabolism, and was the first glycogen storage disease to be identified—in 1932. The build-up of glycogen causes progressive muscle weakness throughout the body and affects various body tissues, particularly in the heart, skeletal muscles, liver and nervous system. Transmission is by autosomal recessive inheritance. more...

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Children have a 1 in 4 chance of inheriting the disease when both parents carry the abnormal gene. It is estimated to occur in about 1 in 40,000 births.


Pompe disease has three forms defined by age of onset and progression of symptoms:

Infantile, or early onset, is noticed shortly after birth. Symptoms include severe lack of muscle tone, weakness, and enlarged liver and heart. Mental function is not affected. Development appears normal for the first weeks or months but slowly declines as the disease progresses. Swallowing may become difficult and the tongue may protrude and become enlarged. Most children die from respiratory or cardiac complications before 2 years of age.

Juvenile onset symptoms appear in early to late childhood and include progressive weakness of respiratory muscles in the trunk, diaphragm and lower limbs, as well as exercise intolerance. Intelligence is normal. Most patients do not live beyond the second or third decade of life.

Adult onset symptoms also involve generalized muscle weakness and wasting of respiratory muscles in the trunk, lower limbs, and diaphragm. Many patients report respiratory distress, headache at night or upon waking, diminished deep tendon reflexes, and proximal muscle weakness, such as difficulty in climbing stairs. Intellect is not affected. A small number of adult patients live without major symptoms or limitations


Cardiac and respiratory complications are treated symptomatically. Physical and occupational therapy may be beneficial for some patients. Alterations in diet may provide temporary improvement but will not alter the course of the disease. Genetic counseling can provide families with information regarding risk in future pregnancies.


The prognosis for individuals with Pompe disease varies according to the onset and severity of symptoms. The disease is particularly lethal in infants and young children.


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ENZYMES: Genzyme, Pharming Tackle Pompe's Disease
From Applied Genetics News, 8/1/98

Genzyme General (1 Kendall Square, Cambridge, MA 02139-1562; Tel: 617/252-7500) and Pharming Group N.V. (Leiden, Netherlands) are forming a joint venture to develop and commercialize the enzyme human alpha-glucosidase as a treatment for Pompe's disease.

This condition is a fatal type of lysosomal storage disorder, caused by a complete or partial deficiency of alpha-glucosidase. The disease results in a build-up of glycogen in various muscles and organs of the body, leading to fatal muscle degeneration. Pharming believes that administration of human alpha-glucosidase to patients suffering from Pompe's disease could alleviate or eliminate symptoms.

Human alpha-glucosidase, which is secreted in the milk of transgenic rabbits, is Pharming's lead product. In June 1998, Pharming announced preliminary results from a completed Phase I clinical trial with human alpha-glucosidase. The trial was designed to determine the safety, tolerability, and pharmacokinetics of the compound in healthy volunteers.

Based on the results obtained in the phase I trial and in pre-clinical studies, Pharming expects to commence Phase II/III clinical trials later in 1998. Pharming was granted orphan drug designation for human alpha-glucosidase by the FDA in September 1996, potentially giving the product market exclusivity in the United States for seven years following FDA approval.

Pompe's disease is one of a family of 40 rare diseases known generally as lysosomal storage disorders. Pompe's disease, also known as acid maltase deficiency or glycogen storage disorder type II, affects an estimated 5,000-10,000 people in the western world. Clinical forms of Pompe's disease vary according to the age of onset and progression of symptoms.

The infantile form appears in the first few months after birth and is characterized by a rapid build-up of glycogen in several tissues, severe muscle weakness, and enlargement of the heart and liver. Respiratory and heart complications often lead to death before the age of two.

The juvenile form usually begins in early childhood and develops more slowly. It is characterized by progressive muscle weakness, with the respiratory muscles being most critically affected. Patients with this form of the disease usually succumb to respiratory failure before the third decade of life.

In the adult form of the disease, symptoms begin to appear between the second and sixth decades of life. Glycogen build-up occurs mainly in skeletal muscle, leading to muscular weakness, particularly in the diaphragm, limb girdle, and the trunk. Respiratory complications are the main cause of death.

Besides contributing to the joint venture, Genzyme will make an equity investment in Pharming of $14 million.

Genzyme appears to have broad commitment to enzyme deficiency diseases. It already markets "Ceredase" and Cerezyme" versions of glucocerebrosidase, worth $333 million in sales in 1997. The company recently announced that it planned to work with BioMarin Pharmaceutical (11 Pimental Court, Novato, CA 94949; Tel: 415/382- 6653) to develop alpha-L-iduronidase as a treatment for Hurler's syndrome, another lysosomal storage disorder. In addition, it is conducting a Phase I/II clinical trial of alpha-galactosidase as a treatment for Fabry's disease. Genzyme also is investigating gene- therapy approaches to treating lysosomal storage disorders.

Pharming specializes in the development, production, and commercialization of human therapeutic proteins, produced at high levels in the milk of transgenic animals that have been created using the company's proprietary technology.

COPYRIGHT 1998 Business Communications Company, Inc.
COPYRIGHT 2004 Gale Group

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