[Pitfalls of monoclonal gammopathy]

Monoclonal gammopathy of undetermined significance (MGUS) is a frequent condition affecting at least 3% of the general population over 50 years. Usually, the diagnosis of MGUS is made accidentally during a biological assessment for other conditions. Although MGUS is most frequently a benign and asymptomatic disorder, it has well been described that MGUS could be a premalignant status and that the risk of transformation into myeloma or other lymphoproliferative disorders is estimated at 1% per year. MGUS can also be associated with other diseases than malignant disorders such as Infections, autoimmune diseases. In some case it could reflect rare but severe disorders that will be crucial not to miss the diagnosis.