ObjectivesGlycogen storage disease type Ia (GSD-Ia), a congenital deficiency of hepatic glucose-6-phosphatase activity, is often associated with hyperproteinemia. To document the mechanism of hyperproteinemia, the proteins of the hemostatic system were analyzed according to their site of synthesis: hepatocyte, endothelial cell, or both. The role of inflammation was investigated by the measurement of tumor necrosis factor alpha (TNF-&agr;) and interleukin-6 (IL-6) levels in plasma.MethodsTwenty-seven patients with GSD-Ia were evaluated, as were 14 patients with other types of GSD and 30 healthy control subjects. Of the 41 patients with GSD, 15 also had hepatic adenoma (14 patients with GSD-Ia and 1 with GSD type III).ResultsIn patients with GSD-Ia, there was a two-fold increase in all hepatocyte-synthesized proteins (i.e., factor VII, protein C, C4b binding protein) compared with control subjects and patients with other types of GSD. The proteins with mixed endothelial and hepatocyte origin (i.e., antithrombin and protein S) also were significantly increased but to a lesser extent. In contrast, the mean concentration of von Willebrand factor, which is exclusively synthesized in endothelial cells, was normal, as was the concentration of TNF-&agr; and IL-6.ConclusionsThese results suggest that the hyperproteinemia of GSD-Ia (including hemostatic proteins) is attributable to hepatocyte dysfunction and not related to an inflammatory process.