Pompe disease is a disorder of metabolism first described in 1932 by Dr J C Pompe. The main issue in Pompe disease is that there is a lack of the enzyme, called acid alpha-glucosidase (GAA) which is responsible for degrading glycogen inside the lysosome of the cells.

Consequently, cells cannot obtain energy from glycogen, and this is accumulated inside the lysosome of the cells of the body, mainly in the skeletal muscle and the heart, but also in neurons. Lysosomes are found in almost all cells in the body. An essential enzyme for the metabolism of glycogen called acid alpha-glucosidase (GAA) is deficient or dysfunctional within the lysosome.

It is a rare neuromuscular, genetic condition that occurs in babies, children and adults who inherit a defective gene from each of their parents. Though the genetic defect that causes GSD2 is present at birth, symptoms may appear at any time from birth to adulthood.

Pompe is now sometimes referred to as GSD2a, because Danon disease is sometimes known as GSD2b even though it involves a different gene. Read our information on Danon disease

 

Pompe disease has two forms, so it is important to check which one you are learning or reading about.

The two forms are infantile-onset Pompe disease and late-onset Pompe disease.

In the case of infantile-onset Pompe disease, patients do not express any GAA enzyme at all and develop symptoms very early in life, during the first months after birth. Symptoms consist of generalized muscle weakness, floppiness, swallowing difficulties, and respiratory and cardiac insufficiency. Cardiac problems are the most severe symptoms in these cases; if the patients are not treated, they could lead to death. Fortunately, enzymatic replacement, which is the standard for care treatment of this disease reverts cardiac problems extending the life of patients and leading to a variable degree of improvement in skeletal muscle weakness.

Late-onset Pompe disease patients present very heterogeneously, ranging from just isolated hyperCKemia (an increase in creatin-kinase levels in blood not associated with any symptom) to limb-girdle progressive muscle weakness. Most of the patients develop muscle weakness during their life that is variable in severity and tend to associate with respiratory involvement. Treatment with ERT has a positive impact on the disease, mainly slowing down disease progression, although muscle weakness could continue to progress despite the treatment.