Late onset glycogen storage disease type II: pitfalls in the diagnosis

Glycogen storage disease type II (GSD-II) is a lysosomal disorder caused by acid α glucosidase (GAA) deficiency. The infantile form is easier to recognize compared with the milder adult form that may manifest as myopathy without specific clinical characteristics. The aim of this study is to highlight frequent diagnostic errors in adult GSD-II patients.

We report four patients with confirmed GSD-II who were at first diagnosed with hypothyroid myopathy, connective tissue disorder, an underlying liver disease and muscular dystrophy, respectively.

Internists but even neurologists with low suspicion may misdiagnose GSD-II. The early respiratory involvement and the characteristic laboratory abnormalities in a myopathic patient should include GAA deficiency in the differential diagnosis especially in the era of enzyme replacement therapy.