Late Infantile Acid Maltase Deficiency

CLASSICAL type II glycogenosis is a hereditary generalized glycogen storage disease,¹⁻³appearing in the first few months of life. The disease is characterized by profound weakness, hypotonia, and cardiomegaly followed by failure to thrive, progressive cardiorespiratory failure, and death. Glycogen is deposited in numerous tissues including brain and spinal cord. Most patients die within the first year of life. In 1963, Hers⁴described the absence of α-1, 4-glucosidase, (acid maltase) in tissues of infants with type II glycogenosis. Recently, deficiencies of acid maltase have been found in individuals with clinical manifestations different from infants with classical type II glycogenosis. There have been reports of five children with acid maltase deficiency and progressive weakness but no cardiac or visceral symptoms, surviving beyond infancy.⁵⁻⁸ This communication describes a patient with acid maltase deficiency whose only symptoms were due to a moderately severe myopathy at age 4 years.⁹