Background: Hemangioblastomas express erythropoietin and the patients often present with polycythemia.
Methods: Serum erythropoietin was measured using a commercial immunoassay, a functional erythropoietin assay and iso-electric focusing.
Results: Despite the polycythemia, serum erythropoietin remained low, while a functional erythropoietin-assay showed a 4-5 higher activity in serum compared to the immunoassay. Iso-electric focusing of serum erythropoietin indicated overrepresentation of highly sialylated erythropoietin isoforms produced by the tumor. As a result, altered affinity of the monoclonal antibody used in the immunoassay for the hypersialylated isoforms was suggested.
Conclusion: Analysis of erythropoietin isoforms may be helpful in distinguishing the ectopic erythropoietin isoforms from normally glycosylated erythropoietin.
Keywords: Erythropoietin isoforms; Glycosylation; Hemangioblastoma; von Hippel–Lindau.
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