Adult polyglucosan body disease with reduced glycogen branching enzyme activity and heterozygous GBE1 mutation mimicking a low-grade glioma

Adult polyglucosan body disease (APBD) is a rare neurologic disease characterized clinically by progressive upper and lower motor neuron dysfunction, neurogenic bladder, distal sensory loss, cerebellar dysfunction and dementia, while histologically featured by diffuse accumulation of polyglucosan bodies throughout the nervous system and in other organs. In some cases, this entity has been proved to be associated with reduced activity of glycogen branching enzyme and mutations of GBE1. We are reporting here a case of adult polyglucosan body disease with an atypical clinical presentation and imaging features that mimic a low-grade glioma. On enzymatic studies, there was reduced activity of glycogen branching enzyme in muscle but normal glycogen content. We also identified a heterozygous consensus splice site variant in intron 5 (c.691+2T>C) and a homozygous variant of unknown significance (c.-35dupC). Our case illustrates the possible clinical, imaging, pathologic, and genetic diversity of APBD.