The "muscular variant" of Pompe disease: clinical, biochemical and histologic characteristics.

We report on a 2-yr-old boy with progressive muscular weakness and respiratory failure. There was no clinical evidence of heart muscle involvement. Autopsy showed marked intralysosomal glycogen deposition in skeletal muscle and liver with no histological evidence of glycogen deposition in cardiac muscle. The activity of the lysosomal enzyme alpha-1,4-glucosidase was deficient in skin fibroblasts, skeletal muscle, cardiac muscle, and liver; however, the enzymatic activity in peripheral blood leukocytes was in the low normal range. The child's mother had normal enzymatic activity in leukocytes but heterozygote levels in skin fibroblasts.