Polycythemia vera (PV) is a rare acquired myeloproliferative neoplasm that causes an overproduction of erythrocytes, leukocytes, and platelets and is a risk factor for systemic thromboses and ischemic stroke. The term “hyperviscosity syndrome” refers to hematologic and neurologic disturbance as a result of platelet dysfunction from the overproduction of serum proteins. Hyperproteinemia occurs in myelomas, polyclonal gammopathies, and iatrogenically via the administration of human intravenous immunoglobulin (IVIg). IVIg has been associated with ischemic strokes, thromboembolism formation, vasculitis, and cerebral artery vasospasm.

In a case report by Byrne, et al. (Neurology, 2002), a 70-year old woman with PV, who was diagnosed with Guillain-Barré Syndrome (GBS), was treated with IVIg and subsequently developed large bilateral middle cerebral artery territory infarctions. Post-mortem analysis revealed intravascular platelet-fibrin IgG thrombi within the areas of infarct. IVIg administration in this patient with PV was thought to be the cause of the ischemic strokes and the catastrophic outcome.

PLEX was performed with an ensuing plateau of motor weakness without any adverse outcomes, along with the co-administration of aspirin, hydroxyurea, phlebotomy, and appropriate DVT prophylaxis. At 1-month and 3-month follow-ups, he demonstrated gradual recovery in motor and sensory deficits.

In patients with myeloproliferative disorders such as PV who require acute immunomodulatory therapy, it may be reasonable to favor PLEX over IVIg or other specific antibody infusions, as PLEX along with standard supportive care, may possess a lower risk of systemic thromboses and stroke.