[Familial Mediterranean fever and myeloma: an undescribed association].

An atypical case of familial mediterranean fever is presented in a 55 year old male with neither family antecedents nor ethnic determinants. The patient presented isolated articular involvement and positive response in the metaraminol provocation and colchicine suppression test. It was associated with monoclonal type IgG kappa gammopathy which evolved over one year until obtaining criteria, although asymptomatic, for myeloma. The increase of the monoclonal component and the infiltration of the bone medulla by plasmatic cells were considered as signs of progression inducing the initiation of treatment despite the lack of symptoms. Both entities are discussed and a mechanism justifying their association is proposed: interleukin-6 produced by macrophages in the inflammatory articular foci due to the deficiency of the C5a inhibitor existing in familial mediterranean fever, may act on a plasmatic cell clone in which receptors for IL-6 exist as a paracrine growth factor.