McArdle’s Disease

McArdle ‘s disease is an energy utilization disorder with a genetic cause. People have dark urine, muscle weakness, cramps, and skeletal muscle stiffness. So far, McArdle’s disease has been incurable and is only treated symptomatically with dietary and physiotherapeutic therapies.

McArdle’s Disease

What is McArdle disease?

McArdle disease is also known as McArdle myopathy, McArdle disease or McArdle syndrome. Sometimes the energy utilization disease is also referred to as the glycogen storage disease type V. McArdle’s disease is named after Brian McArdle. In 1951, the pediatrician documented a defect in alpha-glucan phosphorylase for the first time. See homethodology for Membranous Glomerulonephritis Overview.

This is the isoform of the enzyme glycogen phosphorylase. This enzyme is found specifically in the human skeletal muscles, where it is responsible for glucose utilization. A genetic defect can impair the activity of glycogen phosphorylase and thus trigger an energy utilization disorder. The body stores the energy source glucose in the muscles in the form of glycogen. Glycogen phosphorylase recycles glycogen into glucose residues. The enzyme thus provides the body with material for energy production during glycolysis or the oxidative citric acid cycle. This supply process is disrupted in McArdle disease.


McArdle’s disease is based on a genetic defect and is a relatively rare hereditary disease. The genetic enzyme defect disrupts the de-storage of glycogen to glucose. As a result, glycogen accumulates and the body is no longer supplied with sufficient energy. The term PGYM mutation is often mentioned in the causal connection with McArdle’s disease.

McArdle disease is inherited in an autosomal recessive manner. Thus, only the offspring of two carriers of the genetic defect can develop the phenomenon. The probability of this is one in four for two carriers of the gene defect. However, there is an equally high probability of having a healthy child. The probability of a symptom-free child with the gene defect is estimated at a ratio of around two to four.

Symptoms, Ailments & Signs

McArdle syndrome usually makes itself felt in the early years in the form of tiredness and exhaustion. Symptoms often appear in young adulthood at the latest. The energy utilization disorder is most noticeable in the skeletal muscles. Reduced muscle resilience, muscle cramps, stiffness and muscle pain are among the most common early symptoms.

Many patients also report dark discoloration of the urine. This discoloration is usually due to muscle breakdown products in the context of increasing muscle damage. The symptoms described usually occur after extreme exertion or with sustained muscle exertion such as hiking.

Patients with McArdle’s disease do not have to be permanently affected by the symptoms of the disease. The complaints usually subside. Often there is an improvement after about ten minutes. This improvement is related to the conversion of the muscle’s own energy metabolism. Even short breaks can often temporarily reduce the symptoms.

Diagnosis & course of disease

Diagnosing McArdle disease is challenging. In terms of the medical history, the stress pain in the muscles plays a particularly important role. This pain can be assessed more closely using a muscle stress test. However, they are extremely unspecific and therefore actually not sufficient evidence of McArdle’s disease.

Elevated creatine kinase is often found in the serum of patients with this hereditary disease. Elevated levels of uric acid and ammonia can also be pathological and speak for McArdle’s disease. However, these factors are also rather unspecific and also occur in other enzyme disorders. Therefore, if a doctor suspects McArdle disease, he or she will usually order a muscle biopsy. In this biopsy, the detection of glycogen deposits in the muscle fibers is considered to confirm the diagnosis.

The diagnosis is supported by a non-reacting or hardly reacting phosphorylase in terms of enzyme histochemistry. A PGYM mutation can be detected in molecular genetic studies. The prognosis for McArdle disease is good. For example, the disease is not associated with a noticeably reduced life expectancy.


In most cases, those affected by McArdle’s disease suffer from very pronounced tiredness and exhaustion. The patient’s resilience also drops significantly, leading to exhaustion and, not infrequently, exclusion from social life. Muscle cramps also occur and those affected appear stiff and immobile.

The muscles themselves can also hurt and thus lead to various restrictions in everyday life. It is not uncommon for the pain to also occur at night in the form of rest pain and lead to sleep disorders. Pain and swelling occur, especially under heavy loads.

However, the symptoms themselves are not permanent and disappear after a short time. However, the permanent stress-related pain leads to a significant reduction in the patient’s quality of life. However, life expectancy is not limited by McArdle’s disease.

The symptoms can be treated and limited with various therapies and training. There are no particular complications. However, a causal treatment of this disease is not possible.

When should you go to the doctor?

As a rare glycogen storage disease, McArdle disease is rarely correctly diagnosed before the age of 30. The metabolic disease glycogenosis type 5 manifests itself mainly through muscle pain. These occur even with light and short exercise intensity.

These symptoms of McArdle’s disease are often underestimated or misinterpreted by those affected or by doctors. Those affected often treat such muscle problems by rest or magnesium supplements. Even if those affected go to the doctor in good time, it is often of no use to them. If the disease progresses without treatment, the muscular problems increase. Cramps, myalgia or severe muscular exhaustion occur. Many muscle cells have now been destroyed by glycogen storage problems.

So far, only symptomatic treatment of McArdle’s disease has been feasible. Before physical exertion, a ketogenic diet can have a symptom-relieving effect. With endurance training, the individual stress limit is maintained. Without special knowledge about the nature of the disease, those affected can hardly behave properly. Even with a known diagnosis and medical or physiotherapeutic treatment, nothing more than alleviation of symptoms can be achieved.

Treatment & Therapy

The cause of McArdle’s disease cannot yet be cured. Therefore, only symptomatic therapies are currently available for treatment. This includes, above all, a dietary approach. Patients should actively consume glucose and fructose, especially shortly before or during stress phases. This measure is usually combined with stress therapy. For example, permanent muscle weakness can be reduced by physiotherapeutic measures in combination with dietary measures.

In this context, the anaerobic threshold plays an important role. According to studies, endurance training below this threshold has been able to achieve the best results. The anaerobic threshold is the balance between the breakdown and formation of lactate. Endurance training as a therapeutic measure for McArdle’s disease should therefore take place under the maximum load intensity. In individual cases, medicinal therapies are also used as a therapeutic measure.

This includes, above all, the administration of low-dose creatine. This drug treatment has resulted in a significant improvement in the performance of patients in clinical studies. Since gene therapy is of great importance in modern research, it may be possible to develop a causal treatment option for McArdle’s disease within the next few decades.

Outlook & Forecast

The life expectancy of those affected with McArdle’s disease will not be reduced. In most cases, the disease causes the patients to suffer from very pronounced tiredness and permanent exhaustion. The resilience of those affected also drops significantly and exhaustion often occurs. This often leads to a real exclusion from everyday social life. Muscle cramps can also occur, making the patient appear very stiff and unnaturally immobile. The muscles themselves can also hurt a lot and thus lead to various restrictions in the patient’s everyday life. This pain often occurs during sleep at night.

In the form of rest pain, they often lead to severe sleep disorders. Swelling and pain can occur in the patient, especially under very heavy loads. However, these symptoms are not permanent. They often disappear again after a short time, as if by themselves. However, the permanent stress-related pain in patients leads to a significantly reduced quality of life.

However, the symptoms can be treated and slowed down. This is done with the help of various therapies and special training. There are no significant complications in McArdle’s disease. However, a complete cure of the disease is not possible.


McArdle disease cannot be prevented because it is an automal recessive inherited disease.


Follow-up care for McArdle disease usually proves to be relatively difficult, with in some cases very few or no special follow-up measures being available to the sufferer. Since it is a genetic disease, it cannot be completely cured. Those affected should therefore have a genetic test and counseling carried out if they wish to have children in order to be able to better assess the risk of the disease being passed on to offspring.

As a rule, those affected by this disease are dependent on the help and care of their own family, whereby loving and intensive conversations are also very important. This can prevent depression and other mental upsets. Likewise, the measures of physiotherapy or physiotherapy are very important to alleviate and limit the symptoms of McArdle’s disease.

The person concerned can repeat many exercises from such therapies at home and thus increase mobility. In many cases with McArdle’s disease, contact with other people affected by the disease is also very useful, as this can lead to an exchange of information, which makes everyday life easier for the person affected. As a rule, the life expectancy of the patient from this disease remains unchanged.

You can do that yourself

Dietary measures are at the forefront of therapy. The patient must follow a healthy diet rich in glucose or fructose. Especially shortly before or during physical exertion, the healing process can be positively influenced by the supply of the appropriate substances. In addition, alcohol and caffeine should be avoided. Ideally, the nutrition plan is drawn up together with the responsible doctor and a nutrition expert.

Since McArdle’s disease mainly affects the muscles, sport should be practiced. Endurance training below the anaerobic threshold can significantly improve performance. In connection with a creatine treatment, the muscle complaints can be effectively reduced. The other self-help measures focus on a healthy lifestyle with sufficient exercise, a balanced diet and avoiding stress. Above all, physical stress should be avoided, as this can quickly lead to a worsening of the symptoms.

Patients who have severe muscle problems despite the measures mentioned are best advised to speak to the responsible doctor. Creatine therapy often has to be adjusted again or supplemented with other preparations. Alternative measures such as massages or acupuncture can also help in individual cases with McArdle’s disease.