Pompe disease is a rare (estimated at 1 in every 40,000 births), inherited and often fatal disorder that disables the heart and skeletal muscles.  It is caused by mutations in a gene that makes an enzyme called acid alpha-glucosidase (GAA).  Normally, the body uses GAA to break down glycogen, a stored form of sugar used for energy. Infantile Pompe disease is the result of complete or near complete deficiency of GAA.  Symptoms begin in the first months of life, with feeding problems, poor weight gain, muscle weakness, floppiness, and head lag. Respiratory difficulties are often complicated by lung infections.  The heart is grossly enlarged. Many infants with Pompe disease also have enlarged tongues.  Without enzyme replacement therapy, the hearts of babies with infantile onset Pompe disease progressively thicken and enlarge.   Most babies die from cardiac or respiratory complications before their first birthday.  Juvenile/Adult Pompe disease is the result of a partial deficiency of GAA.  The onset can be as early as the first decade of childhood or as late as the sixth decade of adulthood.  The primary symptom is muscle weakness progressing to respiratory weakness and death from respiratory failure after a course lasting several years.  The heart is usually not involved.    In general, the later the age of onset, the slower the progression of the disease.  Ultimately, the prognosis is dependent upon the extent of respiratory muscle involvement. A diagnosis of Pompe disease can be confirmed by screening for the common genetic mutations or measuring the level of GAA enzyme activity in a blood sample.   Once Pompe disease is diagnosed, testing of all family members and a consultation with a professional geneticist are recommended.  Carriers are most reliably identified via genetic mutation analysis.