Pompe disease

Pompe disease is one of the congenital metabolic diseases that you can encounter. This disease is a lysomal glycocene storage disease. The course of the disease is progressive and adequate treatment has only just become available in the form of therapy with Myozyme. A large part of the treatment of Pompe disease consists of controlling and alleviating the symptoms.

What is Pompe disease?

Pompe disease is an inborn error of metabolism that causes muscle disease. Pompe disease belongs to both glycogen and lysosomal storage diseases. Glycocene storage disease is an umbrella term for conditions that prevent glycocene from being sufficiently broken down by the body. The cause of this is often a change in the hereditary material. Pompe disease is the only lysosomal glycocene storage disease .

What is glycocene?

Glycocene is the form in which sugars are stored in the muscles and liver. This substance is used up with the help of certain enzymes. When one of these enzymes does not function properly or is even absent, glycocene cannot be broken down sufficiently or not at all by the body. This causes the accumulation of glycocene in the cells. In Pompe disease, the enzyme ‘acid maltase’ , also called ‘alpha-glucosidase’ , does not work or does not work sufficiently.

Consequences of glycocene accumulation

The accumulation of glycocene in the cells is toxic . It causes impaired functioning of the lysosome , and ultimately of the entire cell. The lysosome is a vesicle located in the cytoplasm of a cell where it functions as the cell’s ‘garbage dump’. Lysomal enzymes break down various substances, allowing these substances to be reused or excreted. Because the accumulation of glycocene is toxic, the functioning of the lysosome is made more difficult, ultimately making the entire cell function more difficult. This causes damage to tissues and organs because the cell can no longer function properly.

Muscle weakness

The accumulation of glycocene mainly takes place in the muscles. This causes muscle weakness. Pompe disease has three types:

  1. The infantile form: occurs in babies
  2. The juvenile form: first symptoms occur in childhood
  3. Adult form: first symptoms appear in adulthood

The infantile form is usually the most severe. The muscle weakness increases very strongly and quickly and the heart of these children is often enlarged.

Prevalence

Pompe disease occurs on average in 1 in 40,000 people. Pompe disease is a hereditary condition ; inheritance is autosomal recessive. This means that if both parents are carriers of the disease (but do not suffer from it themselves), each child of these parents has a 25% chance of developing Pompe disease. The disease is caused by a mutation in the chromosomes that are important in the production of ‘alpha-glucosidase’ .

Symptoms

The symptoms may develop in early childhood or later in life. There are major differences in the course of the disease, but in general the earlier the symptoms develop, the faster and more serious the course of the disease. Many people with Pompe disease have reduced muscle strength , in the early stages especially in the back and pelvic muscles. These symptoms develop very gradually , which means that a diagnosis is often made late. Children often have difficulty with activities in gym class, such as running or push-ups. However, the symptoms usually only become bothersome when one starts to have difficulty getting up from a sitting position, has difficulty turning over in bed or is unable to get up after a fall. In young people, a deformity of the spine can occur, this is called scoliosis . The muscle weakness increases progressively , so that at a certain point one can no longer stand, walk, sit, etc. independently. The disease takes over your life. In many patients, the respiratory muscles are also affected. Sometimes this is even the first noticeable phenomenon. This can cause problems with eating due to difficulty swallowing and fatigue.

Diagnosis

The diagnosis is made after extensive physical examination . The preliminary diagnosis can be confirmed with the help of a blood test . This blood test examines the activity of certain enzymes that are considered to be involved in Pompe disease. A muscle biopsy is often also performed. Pieces of muscle tissue are taken and examined microscopically for abnormalities. In Pompe disease, small spaces are often found in the muscle cells that are filled with glycocene. It is also possible to detect Pompe disease by means of a prenatal test . Chorionic villus sampling or amniocentesis is used for this. It is also possible to use a DNA test to determine whether you are a carrier of Pompe disease.

Therapy

Pompe disease cannot (almost) be cured. However, there are various therapies in development that could possibly lead to a cure.

Therapy with Myozyme

Since the beginning of 2006, an officially registered medicine has been on the market: enzyme replacement therapy with Myozyme . This treatment is accessible to all people with Pompe disease. The treatment takes place at the Erasmus Medical Center in Rotterdam and is fully reimbursed by insurance companies. With this treatment, Myozyme is administered intravenously for one day every two weeks. This treatment must be continued for the rest of life. Myozyme is a biotechnologically produced form of the human enzyme ‘alpha-glucosidase’ and, when administered, ensures that patients can break down glycocene again. The precise effect of Myozyme is not yet known. A lot of research is therefore being conducted into this substance.

Research

Two possible treatment options are currently being investigated for Pompe disease: gene therapy and chaperone therapy. In gene therapy , the aim is to copy the gene that codes for the missing enzyme and introduce it into the body cells, causing the enzyme to be produced again. With chaperone therapy it is assumed that too little glycogen is transferred because many of the enzymes produced are not suitable. With the help of chaperone therapy, these rejected enzymes are modified in such a way that they are suitable and can do their work.

Combating consequences

Because there are no suitable curative therapies other than therapy with Myozyme, treatment mainly consists of combating and mitigating the consequences . Physiotherapy can strengthen the muscles. If you experience breathing problems, you can consider breathing support with home ventilation equipment. A high-protein diet can improve breathing and reduce muscle breakdown. Some patients indicate that they benefit from regular administration of glucose.

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