Pompe disease is also known as glycogen storage disease type II (GSD II) or acid maltase deficiency is a genetic disorder that causes increasing muscular weakness.
Pompe disease is a condition in which the body is not able to break down complex sugar, which subsequently affects organs and tissues especially tissues of the muscles.
It is a very genetic condition that affects around 1 in 40,000 childbirth and most parents must carry the abnormal or mutated gene; in other words, it is a recessive genetic condition.
The condition was first described in 1932 by Dutch pathologist, Johannes Pompe. He made a connection that the disease was caused by a buildup of glycogen in muscle tissues, this accumulation of glycogen was the cause of the common symptom of the disease; progressive muscular weakness all over the body.
Johannes Pompe was presented with a 7-month-old girl who died after developing idiopathic hypertrophic cardiomyopathy. Pompe made a puzzling observation of an abnormal accumulation of glycogen in all examined tissues of the body and described the exact pathologic features of this lysosomal storage disorder.
Pompe disease is grouped as a type of metabolic disease called lysosomal storage disorders (LSDs). These conditions like Pompe disease result from a deficiency of acid alpha-glucosidase (acid maltase), a lysosomal hydrolase.
The primary function of acid alpha-glucosidase in the cell is to convert glycogen within the lysosomes to glucose. Shedding further light on Pompe disease, was a Belgian scientist, Christian de Duve while researching insulin, discovered the cell structures- lysosomes in 1955.
Dr. Christian Duve uncovered that lysosomes had their own specific set of enzymes for breaking down glucose and recycling cellular components.
This discovery made him a Noble prize winner in his field in 1974. Extensive research by Duve’s colleague, Henri Hers revealed a deficiency inside lysosomes of GAA (acid alpha-glucosidase); the enzyme that breaks down glycogen and this explained the symptoms experienced in Pompe disease. Henri Hers was the one who established that Pompe’s disease is a lysosomal storage disorder (LSD).
The disease is not limited to any race nor ethnicity and it can happen to anyone, but statistics data reveal it is more common in African American and some Asian groups.
Classification of Pompe Disease
Pompe disease is classified based on its onset in the stage of life of an individual (age onset), severity, organ involvement, and rate of disease progression.
Based on age onset is the major classification of Pompe disease and there are three main classifications in this category:
- Classic Infantile onset appears just within a few months after birth
- Non-classic Infantile onset appears at about 1 year of age and
- Late-onset is most rare, and it appears later in a child’s life and may even wait till the teen years or adulthood.
Causes of Pompe Disease
Pompe disease is believed to be gotten only by inheriting it from parents and it is extremely rare to be inherited as both parents must possess the flawed genes and pass it down to a child (one from each parent) before a child can be victimized by this genetic disorder.
An individual can possess one flawed gene and not have symptoms of the disease.
This inherited enzyme defect usually manifests in childhood but in few cases, Pompe disease has shown separate adult-onset forms. Generally, glycogen storage diseases (GSDs) are inherited as autosomal recessive disorders, traced to chromosome 17 and several different mutations have been reported for each disease in the category of disorders.
Symptoms of Pompe Disease
Symptoms of Pompe disease may be similar or different in each type of Pompe disease based on age-onset and it differs from individual to individual.
For classic and non-classic early infantile onset, Pompe disease could pose the following symptoms:
- Poor head and neck control
- Breathing difficulties and lung infection
- Trouble eating and no gain in weight.
- Developments in movement like rolling over and sitting up may be delayed.
- Enlarged tongue.
- Enlarged liver.
- Heart defects: enlargement and thickening of the heart.
- Poor muscle tone
- Hearing problems
In a late-onset disease situation, symptoms exhibited may include:
- Enlarged heart.
- Irregular pulse rate
- Loss of the ability to exercise.
- Breathing problems even during sleep
- Increased hearing difficulties
- The legs and the trunk get steadily weaker.
- Progressive difficulty in walking
- Muscle pain over a large area
- Falling often
- The frequent outbreak of lung infection
- Shortness of breath during strenuous activities
- Morning jolts of headaches
- Loss of weight
- Higher levels of creatine kinase (CK); an enzyme that assists the body’s function work and transports usable energy to cells.
- Stiff joints
- Usual curvature in the spine
- Enlarged liver and tongue which makes chewing and swallowing difficult.
This known late-onset of Pompe disease tends to move slowly and it usually involves the heart and liver and their function. It can begin as late as 60 years.
Diagnosis of Pompe Disease
A number of Pompe disease symptoms are similar to symptoms of so many other medical disorders and diseases.
To confirm Pompe disorder, doctors may ask a patient:
- If he/she have hard times breathing especially at night during sleep or when lying down
- If he/she experiences morning headaches
- Feels weak, fall often or have troubles walking, running or doing physical activity.
- Experiences fatigue regularly.
- If the patient is a child, any health issues.
- About Family medical history
If Pompe disease is suspected, tests will be carried out, depending on symptoms exhibited, to rule out other medical conditions.
Often tests to confirm Pompe disease include:
- Checking of blood samples to see how well the “flawed” protein is functioning.
- Checking samples of muscles to measure how much glycogen is contained in the muscle.
- Genetic test to ascertain the genetic problem that causes Pompe disease.
Diagnoses of Pompe disease in an infant can last up to 3months. It can take up to 7-9 years for kids and adults. After confirmation, it is medically advisable for every family member to test for this gene disorder also.
Treatment and Management of Pompe Disease
Prompt and early treatment specifically for infants is the key to holding off damage in the body. Two medications have been researched to replace the missing protein and help the body process sugar normally as it supposes to.
It is administered via injection: Myozyme for infants and Lumizyme for teenagers and adults.
Living with Pompe disease can be very difficult and challenging, medical counselors can be consulted to assist families live with terms of the events and prepare unforeseen outcomes, especially ability changes.
Support groups also can be a good source of practical tips, for example, if people have trouble eating and swallowing, thickeners can be added to food to make it safer to swallow. And need to use feeding tubes to make sure a patient gets enough nutrients.
The infantile early onset of Pompe disease is usually most fatal, with most deaths occurring within 12 months of birth. Enlargement of the heart vessels with increasing obstruction to the left ventricular outflow is the major cause of death in infants.
Another factor that increases the mortality rate is the increasing weakness of the ventilator muscles which increases the risk of pneumonia. Late clinical onset occasionally corresponds with more benign symptoms and disease course.
The late-onset or adult version of Pompe disease manifests with dystrophy (dying of body tissues due to defective nutrition) and respiratory muscle weakness. Respiratory insufficiency is significant morbidity.
However, Glycogen accumulation within blood vessels may lead to intracranial aneurysm (abnormal blood-filled swelling of a vein or an artery in the cranium resulting in localized weakness of the vessel).
Major mortality or morbidity depends on location and clinical nature.
What to expect during Pompe disease? Pompe disease can affect many parts of the body, it is best to see a team of specialists who know the disease, its specificity, and who can help manage the symptoms.
- Cardiologist (heart doctor)
- Neurologist (a doctor who treats the brain, spinal cord, nerve, and muscles)
- Nutritionist, who can assist a patient eat to stay healthy.
- Respiratory therapist (specialist that treat the lungs and their tracts and handling breathing disorders)
Generally, the late onset of Pompe disease is progressively slower than classic and non-classic early onset. Infants can be treated but because the conditions in the symptoms which affect infant is more intense and quickly progressing, they always die in the first year.
There is no particular single cure, but prompt treatments can relieve symptoms and help patients live longer.
- Genetics of Glycogen-Storage Disease; https://emedicine.medscape.com/article/947870-overview
- Pompe Disease; https://www.ninds.nih.gov/Disorders/All-Disorders/Pompe-Disease-Information-Page
- Pompe Disease; http://my.clevelandclinic.org/health/diseases/15808-pompe-disease
- Pompe Disease; http://rarediseases.org/rare-diseases/pompe-disease