Glycogen Storage Disorder due to Glycogen Branching Enzyme (GBE) Deficiency: A Diagnostic Dilemma

Glycogen storage disease type IV without detectable polyglucosan bodies: importance of broad gene panels

Glycogen storage disease type IV (GSD IV) is caused by mutations in the glycogen branching enzyme 1 (GBE1) gene and is characterized by accumulation of polyglucosan bodies in liver, muscle and other tissues. We report three cases with neuromuscular forms of GSD IV, none of whom had polyglucosan bodies on muscle biopsy. The first case had no neonatal problems and presented with delayed walking. The other cases presented at birth: one with arthrogryposis, hypotonia, and respiratory distress, the other with talipes and feeding problems. All developed a similar pattern of axial weakness, proximal upper limb weakness and scapular winging, and much milder proximal lower limb weakness. Our cases expand the phenotypic spectrum of neuromuscular GSD IV, highlight that congenital myopathy and limb girdle weakness can be caused by mutations in GBE1, and emphasize that GSD IV should be considered even in the absence of characteristic polyglucosan bodies on muscle biopsy.

Pompe disease: An Indian series diagnosed on muscle biopsy by ultrastructural characterization

Pompe disease (PD) is a lysosomal storage disorder characterized by glycogen accumulation in muscle, with infantile-onset (IOPD) and late-onset (LOPD) types. Nineteen cases of PD were diagnosed over a 14-year period on muscle biopsy by ultrastructural examination. Pools of glycogen (intralysosomal and cytoplasmic) and excessive phagocytosis were seen in myofibers on electron microscopy. Glycogen was noted in endothelial cells in IOPD. Although PD accounts for a small fraction of muscle diseases, timely accurate diagnosis is imperative as it is treatable. Ultrastructural examination is necessary to confirm the diagnosis in cases with non-diagnostic light microscopic features, especially in adult LOPD patients.