Myeloproliferative syndrome evolving in a patient with macromolecular lactate dehydrogenase

A myeloproliferative syndrome, masked by severe iron deficiency, evolved in a woman with lactate dehydrogenase (LDH) complexed to IgA. Macromolecular LDH is an uncommon cause of increased serum LDH activity. By observing the patient's course for ten years, we were able to understand the initially puzzling clinical findings.