Mixed connective tissue disease associated with multicentric Castleman's disease.

We describe a 60-year-old woman who developed mixed connective tissue disease (MCTD) associated with multicentric Castleman's disease (MCD) and Crow-Fukase syndrome (CFS). She showed HLA DR-4 antigen and an abnormal X chromosome (47,XXX). The serum interleukin-6 (IL-6) level was markedly increased and IL-6 mRNA was detected in enlarged lymph node cells. After prednisolone was administered, her IL-6 level decreased and the symptoms of MCTD, MCD, and CFS all improved. Thus, IL-6 may be involved in the modification of the pathologic condition in this patient.