A neonatal form of glycogen storage disease type IV.

We report of an infant with neonatal glycogen storage disease type IV (GSD IV) who was examined for severe hypotonia and cardiomyopathy. On the muscle biopsy there were many fibers with diastase-resistant polyglucosan bodies. Glycogen branching enzyme (GBE1) activity in the muscle was markedly reduced. The infant had a homozygous single nucleotide deletion in the open reading frame of GBE1 gene.