Muscle weakness and poor muscle tone are the primary symptoms of all three types of Pompe disease, a genetic disorder also known as acid maltase deficiency or glycogen storage disease type II.
In Pompe, the acid alpha-glucosidase enzyme does not work properly, so glycogen builds up in the body’s cells. Muscle cells — which use glycogen to help provide energy for movement — are especially affected, which is why the disease is mainly characterized by muscle weakness.
There are three main types of Pompe, which are classified by when symptoms first manifest. When symptoms appear shortly after birth, the condition is called classic infantile Pompe disease. In the non-classic form of Pompe, symptoms appear within the first year of life. When symptoms appear later in childhood or in adulthood, the disease is called late-onset Pompe.
Generally, symptoms tend to be more severe and the disease tends to run a more aggressive course the earlier the symptoms first start to appear.
Symptoms of classic infantile Pompe disease
Infants with this form of Pompe disease experience rapidly progressing muscle weakness and poor muscle tone. These infants may never be able to sit up, crawl, or stand. They may have difficulty breathing, as the muscles required for respiration are weak. The heart muscles in this disease type also are abnormally thick and bulky, leading to a condition called hypertrophic cardiomyopathy, which can result in heart failure, when the heart cannot adequately pump blood to the body’s tissues.
Babies with this type of Pompe often have difficulties with feeding, and may not be able to grow and gain weight at normal rates — a condition known as failure to thrive. They also may have an unusually large, protruding tongue (macroglossia) and hearing problems, and may rest their legs in a “frog position,” a characteristic sign of Pompe.
If untreated, babies with classic infantile Pompe disease usually die within two years of birth, although treatment can improve outcomes.
Symptoms of non-classic infantile Pompe disease
This type of Pompe disease is typically less severe than the classic form. It is marked by babies not achieving developmental milestones such as rolling over or sitting. Although these babies may have a larger-than-normal heart, cardiac complications are less common in this type than in the classic form. Still, muscle weakness is a predominant feature in this form of Pompe disease, and serious breathing problems may develop.
Without treatment, children with non-classic infantile Pompe often survive until early childhood. Treatment may improve outcomes.
Symptoms of late-onset Pompe disease
Children and adults with late-onset Pompe experience muscle weakness, but in these patients it primarily affects the muscles of the shoulders, upper arms, and legs. Typically, the legs are affected more than the arms.
The weakening of the face and throat muscles can cause droopy eyelids and problems with eating and swallowing, leading to gradual weight loss.
Weak muscles surrounding the spine also can cause an abnormal sideways curvature called scoliosis.
Varying degrees of respiratory problems and frequent chest infections may occur due to the weakness of the muscles involved in breathing.
Given the progressive nature of the muscle weakness, it is common for patients to require a wheelchair or a ventilator, which is a machine that supports breathing.
Patients also may experience profound fatigue, as well as muscle pain and cramps. Hearing loss, headaches, and frequent falls also have been reported with this disease type.
Those with late-onset Pompe usually do not have heart problems as serious as those that occur in patients with infantile Pompe. However, they may develop abnormal heart rhythms called arrhythmias.
Last updated: May 19, 2021
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