Definitive prenatal diagnosis for type III glycogen storage disease

Prenatal diagnosis for type III glycogen storage disease was performed by using (1) immunoblot analysis with a polyclonal antibody prepared against purified porcine-muscle debranching enzyme and (2) a qualitative assay for debranching-enzyme activity. Cultured amniotic fluid cells from three pregnancies (three families in which the proband had absence of debrancher protein) were subjected to immunoblot analysis. Two unaffected and one affected fetus were predicted. In addition, cultured amniotic fluid cells from nine pregnancies (eight families) were screened with a qualitative assay based on the persistence of a polysaccharide that has a structure approaching that of a phosphorylase limit dextrin when the cells were exposed to a glucose-free medium. This qualitative assay predicted six unaffected and three affected fetuses. All predictions by either method were confirmed postnatally except for one spontaneously aborted fetus. Our data indicate that a definitive diagnosis of type III glycogen storage disease can be made prenatally by these methods.