Mixed Connective Tissue Disease

Abstract

In the early 1970s, Sharp and colleagues described a series of patients in whom features of Systemic lupus erythematosis (SLE), scleroderma, and inflammatory myositis were found in association with autoantibodies to the U1-ribonucleoprotein (RNP) antigen (1). This syndrome complex was called mixed connective tissue disease (MCTD). Although several classification criteria for MCTD have been published, there remains no universally accepted definition of the condition (2–5). The existence of MCTD as a clinically, immunogenetically, and serologically distinct entity remains a subject of controversy. An excellent review of MCTD and the controversy surrounding its classification has recently been published (6). In support of the concept of MCTD, recent published data demonstrate the distinctive serologic associations of anti-U1-70kD-specific, anti-U1-RNA-specific, and anti-heteronuclear ribonucleoprotein (hnRNP) A2/RA33-specific antibodies with MCTD (7–9). Furthermore, the association of anti-RNP and/or MCTD with the genetic marker HLA-DR4 has been reported from studies done in a number of different countries (6,7,10,11). Finally, it would appear that the concept of MCTD is useful to the clinician regardless of the controversy over nomenclature, because MCTD identifies a group of patients in whom increased surveillance for specific end-organ manifestations may improve patient care (12).