[Late infantile form of Pompe's disease. Deficiency of alpha-1,4-glucosidase (acid maltase)].

Four patients with late infantile form of Pompe's disease, acid maltase deficiency, are presented. In three of them an autosomical recessive genetical transmission was demonstrated. Signs of neuromuscular involvement were present in all of our patients before four years of age. All cases had elevated muscle and liver enzymes. Echocardiographic studies revealed a septal hypertrophy in three patients. Presence of myotonic discharges on EMG examination suggested the diagnosis in three cases. Pathological and biochemical studies of two siblings, one of them aged 14 months, without clinical findings, demonstrated that the enzyme in late infantile form of acid maltase deficiency is missing from birth. Clinical and pathological muscular involvement of case number 4, in front of normal amounts of acid maltase in this muscle, must alert clinicians to perform enzymatic studies in various tissues in order to confirm diagnosis and better understand biochemical basis of the disease.