Besides vacuolated neurons, we found abundant deposition of polyglucosan bodies (PGBs) in the developing brain of this fetus in whom MPS-VII was corroborated by lysosomal beta-glucuronidase-deficiency detected in fetal blood and fetal skin-fibroblasts and by the presence of a heterozygous pathogenic variant in the <i>GUSB</i> gene in the mother. The gene discussed is GUSB; the disease is hyperinsulinemic hypoglycemia, familial, 4.