Pompe Disease

Pompe Disease General Information

Pompe Disease is a metabolic disorder of the autosomal recessive type, which rarely occurs due to a deficiency of a certain enzyme (acid maltase) in the organism. This enzyme is needed in order for the organism to break down the glycogen stored within the body, and the lack of it causes the glycogen to build up in the tissues. This results in the appearance of myopathy (progressive muscle weakness) but it also affects various other types of tissue – such as the liver, heart and nervous system. In most untreated cases, the disease eventually leads to the death as it disables the patient’s heart and muscles

The Pompe Disease is also known as the glycogen storage disease type II, and there are several other variations of this condition. However, this is the only glycogen storage disease that presents a defect in the lysosomal metabolism. This type of the affection has been the first one of its kind to be discovered, in 1932. This affection is genetically inherited through an autosomal recessive pattern. In such cases, both the parents need to have a copy of the defective autosomal gene in order for the affection to be transmitted to the child, and even then, the chances are 1 in 4 for the child to inherit the disorder at birth. That is why this disorder is only rarely encountered, and has an incidence rate of around one in 40,000 births.

Pompe Disease Symptoms

There are three types of Pompe Disease, the classification being made by the age of onset of the affection, and when the symptoms start to appear. These three categories are infantile, juvenile and adult.

The early onset of the disease marks the infantile type of Pompe Disease. In such cases, the symptoms begin to manifest shortly after birth. Severe lack of muscle tone and weakness in the affected child is typically noticed, and examination reveals an enlargement of the heart and liver. Generally, the mental functions in the patients are not affected. The child’s development may appear as normal for a short period, up to a few months, but as the disease progresses the symptoms will start to appear. The tongue may become enlarged and protruding, making swallowing difficult. In most cases, the patient dies within 2 years due to cardiac and respiratory complications.

The juvenile disease typically occurs during childhood, and is commonly manifested as a progressive weakness of the respiratory muscles. The diaphragm and intercostal muscles are most affected, but the weakness may extend to other muscle groups as well, such as the lower limb muscles, making the patient intolerant to most types of exercise.

The adult variation of Pompe Disease also causes general weakness in the patient’s muscles. Respiratory distress is commonly encountered, as well as headaches, diminished reflexes of the deep tendons and weakness of the proximal muscles. A small number of cases has been recorded where the patients did not incur any limitations and were not affected by any major symptoms of the disease.

Pompe Disease Treatment

Once the Pompe Disease has been identified in a patient, the examining health care specialist will provide the patient with information regarding the affection and its complications, as well as present him or her with the therapy options that are available and adequate to his or her case, based on such factors as age, medical history and general health condition. Until recently, this affection did not have any type of curative treatment, but rather a set of therapies that were aiming at improving the patient’s condition and relieving the symptoms of the disease.

In patients that are suffering from Pompe Disease related respiratory or cardiac complications, the affections are treated symptomatically. In some cases, physical therapy may be employed, or occupational therapy, as both may prove beneficial for the patient’s condition. Adjustments in the patient’s diet can be made, however these may only provide a temporary improvement in the patient’s state, and will not affect in any way the course of the disease. Also, genetic counseling is advised for parents suffering from this condition, in order to determine the risks that may be implied in case of pregnancy.

Recently, an enzyme replacement therapy has been made available for patients suffering from Pompe Disease. Prior to that, there was no actual cure for the affection. This therapy however is expensive (around $300,000 a year) and must be continued for the entire life, and this may make it inaccessible to some patients as there have been situations when the insurance companies refused to cover the treatment costs. The treatment involves administration of Myozyme through IV infusion, and this medication is currently available to patients in all the major countries. The effectiveness and the safety of the therapy have been established through two separate trials.

Myozyme treatment is generally carried out in 4 to 5 hour sessions once every two weeks. It is important that the patient makes all the arrangements – for example at work or in school – to ensure that he or she will be able to be present at these sessions, as it is very important that the Pompe Disease therapy is continued for the entire life. In some cases, the patient may discuss with the health care specialist the possibility of delaying a session, but this may only be done with the approval of the specialized health care professional as the situation must be assessed in order to ensure that this delay will not have a strong negative impact on the patient’s condition. In case the situation is approved by the examining physician, missed or delayed doses will be administered as soon as possible or in other ways made up for. Generally, and especially at the beginning of the treatment, the enzyme replacement therapy is performed at the hospital, however in certain circumstances the patient may receive approval for the therapy to continue in the comfort of their home.

There have been reports that other enzyme replacement therapies for Pompe Disease are currently being researched, that are aiming to obtain curative solutions through other means – for example, the one based on GILT (glycosylation independent lysosomal targeting technology).