Pompe disease

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at January 2, 2017
StartDiseasesPompe disease

Pompe disease is an uncommon but serious condition characterized by muscle weakness that progresses over time. Individuals with the disease experience a variety of symptoms that are usually related to difficulty breathing and difficulty walking. Being diagnosed by a doctor is essential for managing the symptoms of the disease.

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Definition & Facts

Pompe disease is a rare disorder that affects about 1 in every 40,000 people in the United States. The symptoms of the disease vary from person to person, but it always results in muscle weakness that worsens over time.

The disease affects men and women equally, but it appears more frequently in African Americans and people from Taiwan and China. Most doctors classify Pompe disease as a neuromuscular disease, but it can also be identified as a genetic disorder, a cardiovascular disease, and a metabolic muscle disease.

Symptoms & Complaints

Symptoms can appear at any time during an individual's life. Some people experience the symptoms starting in infancy or childhood, and some people don't notice any symptoms until adulthood. Pompe disease always progressively worsens, but the rate of progression can vary.

Typically, the earlier the symptoms appear, the worse the disease will eventually become. However, rapid decline can occur at any time during an individual's life. The most common symptoms in infants with Pompe disease are extreme muscle weakness, an enlarged heart (cardiomegaly), and trouble feeding. Because of the muscle weakness, infants often do not meeting normal developmental milestones like rolling over and sitting up.

The primary symptoms in children and adults are difficulty with mobility and breathing problems. People with Pompe disease often feel winded after climbing a flight of stairs and have trouble breathing while lying down. Some people with the disease also feel weakness in their arms and legs and may fall asleep in the middle of the day. Heart problems are much less common in adults than in infants and younger children with the disease. 

Causes

Pompe disease is always caused by a defective gene. Individuals with the disease have a deficiency of acid alpha-glucosidase, or GAA. GAA is an enzyme responsible for breaking down glycogen, a sugar stored in the muscle cells. When people have a deficiency in GAA or lack GAA, glycogen builds up in the muscle cells. As the glycogen builds up, the lysosomes in the muscle cells swell, which can hinder muscle functioning and cause weakness. Sometimes, lysosomes can rupture and cause further damage to the muscle cells.

Pompe disease is genetic, so an individual inherits the disease when both parents pass on the mutated GAA gene. If an individual receives the gene from only one parent, they won't have the disease, but they will be a genetic carrier. Carriers can potentially pass the disease to their children. When both parents are carriers, their child has a 25 percent chance of inheriting the disease, a 50 percent chance of becoming a carrier, and a 25 percent chance of not receiving the mutated gene at all. If both parents have Pompe disease, the child will definitely inherit it. 

Diagnosis & Tests

Because Pompe disease has such varying symptoms and can appear at any age, it can be very difficult to diagnose. Many of the common symptoms are characteristic of other diseases, so some people are misdiagnosed. There isn't one test that can always successfully identify Pompe disease, but a few different tests can let doctors know if the disease seems likely.

Heart tests are very common for infants because the heart is almost always affected. Doctors use chest X-rays to check the size of the heart, ECG tests to monitor heart rhythms, and echocardiograms to show any thickening in the heart muscle. In children and adults, doctors often use muscle tests to examine muscle weakness and mobility issues. An EMG test can allow doctors to see electrical activity in the muscles, which can provide information about how the muscles are functioning.

If the patient reports trouble breathing, the doctor can measure his or her lung capacity with pulmonary function tests. When doctors suspect Pompe disease after administering other tests, they can use an enzyme assay, a method of studying enzymes by using a blood sample. With this test, they can determine whether the patient has a GAA deficiency. Some doctors may also perform a muscle biopsy, where they observe a muscle tissue sample to determine whether there is a glycogen buildup.

Treatment & Therapy

There is no cure for Pompe disease, but patients can manage their symptoms with treatment. Most patients work with their doctors to create an individualized treatment plan based on their symptoms. Many patients choose to have comprehensive care, which focuses on managing symptoms in all aspects of life. Care coordinators can arrange a variety of therapies, including physical therapy, respiratory therapy, and occupational therapy. Some individuals with the disease may also see a nutritionist, a speech therapist, or a psychosocial therapist.

Although the disease is rare, most of the general symptoms are common, so there are many treatment options available to manage symptoms and make life more comfortable. For mobility difficulties, patients can use wheelchairs or other supportive equipment. Surgery can sometimes help correct bone issues that result from muscle weakness. For example, some people with Pompe disease develop scoliosis because they have difficulty walking properly.

For breathing issues, patients can use a BiPAP (bilevel positive airway pressure) machine during the day or a CPAP (continuous positive airway pressure) machine as they sleep. If breathing issues become very severe, patients may need a ventilation tool, which is a tube connected to a ventilator that is inserted into the nose or the mouth. To treat the disease itself rather than the symptoms, patients can try enzyme replacement therapy, which raises their GAA levels from an external source.

Prevention & Prophylaxis

Pompe disease is genetic, so it cannot be prevented. However, parents who may be carriers can visit a genetic counselor to discuss their chances of passing the disease to their children. If a child is at risk for the disease because their parents are carriers, awareness of the potential symptoms can help with early diagnosis.

It isn't possible to prevent the disease from worsening, but learning how to manage symptoms during the early stages of the disease can help with symptom management as it progresses.