Adult polyglucosan body disease (APBD) is a rare, inherited neurological disorder characterized by the progressive accumulation of abnormal glycogen-like deposits, known as polyglucosan bodies, within nerve cells. This pathological accumulation leads to a progressive deterioration of neuronal function.

Caused by mutations in the GBE1 gene, APBD results in a deficiency of glycogen branching enzyme. This enzyme is crucial for the normal synthesis of glycogen, a highly branched glucose polymer that serves as an energy storage molecule. Without this enzyme, abnormal glycogen structures accumulate within neurons, disrupting cellular processes and leading to neuronal degeneration.

The clinical presentation of APBD is variable, but commonly includes symptoms such as neurogenic bladder, progressive muscle weakness and spasticity, sensory abnormalities, and cognitive decline. Neurogenic bladder often manifests as urinary incontinence or difficulty emptying the bladder. Muscle weakness and spasticity can lead to difficulties with walking and other movements. Sensory abnormalities, such as numbness or tingling, are frequently reported, particularly in the extremities. As the disease progresses, cognitive impairment, including memory loss and difficulty with thinking and reasoning, may occur.

Radiographic features

T2-weighted and FLAIR imaging demonstrates hyperintensities in the pyramidal tract and medial lemniscus of the medulla and pons. T2-weighted and FLAIR imaging also show bilateral hyperintensities in the cerebral white matter, predominantly involving the periventricular white matter of the occipital and temporal lobes. The posterior limb of the internal capsule and external capsule are frequently involved, while the anterior limb of the internal capsule is typically spared.

MRI reveals spinal cord, medullary, and cerebellar vermis atrophy in all cases, resembling the 'tadpole appearance' characteristic of Alexander disease. FLAIR shows hyperintensity in the pia mater of the medulla, a finding also observed in Alexander disease.