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Keywords:

  • acid α-glucosidase;
  • cross-reactive immunological material;
  • enzyme assay;
  • GAA;
  • Pompe disease

Abstract

Introduction:

Pompe disease (glycogen storage disease type II, acid maltase deficiency) is caused by deficiency of lysosomal acid α-glucosidase (GAA). A few late-onset patients have been reported with skin fibroblast GAA activity levels of <2%.

Methods:

We measured GAA activity in skin fibroblasts from 101 patients with late-onset Pompe disease. Whenever possible, we performed Western blot analysis and correlated the results with GAA activity and GAA gene mutations.

Results:

Thirteen patients (13%) had skin fibroblast GAA activity of <1% of normal. Although there was wide genetic heterogeneity, none of these patients carried the common late-onset mutation c.-32-13T>G. We performed Western blot on 11 patients with <1% GAA activity. All produced GAA protein that was at lower levels and/or was abnormally processed.

Discussion:

There is no common mutation associated with <1% GAA activity in late-onset Pompe disease patients. Most patients produce unprocessed forms of GAA protein compared with patients with higher GAA activity. Muscle Nerve, 2011