Monoclonal gammopathy of undetermined significance evolving directly in primary plasma cell leukemia

A case of monoclonal gammopathy of undetermined significance (MGUS) which evolved directly into primary plasma cell leukemia (PCL) is reported. Even if MGUS and PCL represent the opposite aspects of the same immunoproliferative disorder, no previous cases of this direct evolution have been described, as stated by an accurate review of the specific literature. The patient abruptly developed PCL after five months from the discovery of a serum monoclonal spike, without any other clinical, laboratory and radiological abnormalities. The practical conclusions of this case report indicate that a patient with MGUS must be followed periodically and over an indefinite period, and that PCL must be considered into the possible evolution of MGUS.