An abnormally glycosylated isoform of erythropoietin in hemangioblastoma is associated with polycythemia.

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.