Hyperviscosity syndrome in patients with monoclonal gammopathies is caused by hyperproduction of pathological immunoglobulins. This syndrome is a clinical unit with variety of symptoms that result from hypoperfusion of organs.
We describe two cases of patients suffered for multiple myeloma and hyperviscosity. For treatment of this emergent condition we have to start replacement plasmapheresis as soon as possible, and simultaneously is necessary to start treatment of monoclonal gammopathy.