Monoclonal gammopathy of unknown significance (MGUS) is a common haematological condition. It is characterised by proliferation of a B lymphocyte clone and it's associated antibody (paraprotein). In most cases there are no clinical symptoms, however, in a small number of individuals there may be an interaction of the paraprotein with a molecule expressed by the body (self antigen). This can have effects on the normal function of this molecule and/or cause disease.