Acid Maltase Deficiency
Synonyms: Type II glycogenosis, Pompe disease (denotes infantile form of acid maltase deficiency)
Infantile acid maltase deficiency was first described in 1932 by Pompe and Pultschar. Acid maltase is a lysosomal enzyme, and the deficiency is a type II glycogenosis. The eponym "Pompe disease" should be restricted to the description of the infantile form of the disease.
Three forms: infantile, childhood, and adult-onset disease.
Infantile acid maltase deficiency (Pompe disease)
- diffuse hypotonia and weakness in first weeks-months - "floppy baby syndrome"
- increased muscle bulk
- massive cardiomegaly
- alert, interested in environment
- increased risk for pulmonary infections due to weak respiratory muscles
- death from cardiac or respiratory failure before two years (usually one year)
- small subgroup does not develop cardiopathy and survive to childhood
- normoglycemia and response to epinephrine and glucagon
- elevated serum creatine kinase
- EMG - myopathic features associated with fibrillation potentials, positive waves, bizarre high-frequency discharges, myotonic discharges
- ECG - short P-R interval, giant QRS complexes, LVH/RVH
- CXR - massive cardiac enlargement
Childhood acid maltase deficiency
- begins in infancy or early childhood
- slower progression than the infantile form
- delayed motor milestones
- calf enlargement
- early involvement of respiratory muscles
- death by respiratory failure in 2nd-3rd decade
- no cardiomegaly, less hepatomegaly, less macroglossia
- serum creatine kinase increased to variable degree
- EMG - myopathic features with abnormal irritability and myotonic discharges
Adult acid maltase deficiency
- slowly-progressive myopathy
- starts in 3rd-4th decade, as late as 7th decade
- truncal and proximal muscle weakness
- respiratory muscle weakness also, and may be the presenting complaint
- other presenting complaints include morning headache, exertional dyspnea, sleep-disordered breathing (from diaphragmatic weakness)
- often misdiagnosed as limb-girdle dystrophy or polymyositis
- no visceromegaly
- glycogen accumulation in the smooth muscle of cerebral arteries leads to intracranial aneurysms
- premature atherosclerotic angiopathy of intracerebral vessels leads to TIAs
- intractible fever related to glycogen accumulation in brain neurons
An increased occurrence of cleft lip has been noted with acid maltase deficiency.
EMG is helpful with the occurrence of fibrillation potentials, positive waves, and myotonic discharges.
MRI of muscle to follow the progression of weakness and monitor response to therapeutic trials.
Entry date: June 5, 2005.