Rheumatic diseases with overlapping clinical features have been known since at least 1900 under such descriptive designations as "sclerodermatomyositis," "lupoderma," "rupus," and others. These hybrid descriptors recognize the occasional mixing of features of the classic rheumatic disorders, rheumatoid arthritis, scleroderma, dermatomyositis, and systemic lupus erythematous (SLE), in the same patient. However, because of the absence of precise pathogenetic and etiologic information, even the traditional rheumatic diseases have been largely classified on the basis of aggregations of clinical, histologic, and immunologic findings.
In 1972, Sharp and colleagues first described 26 adults with a new syndrome, which they defined as mixed connective tissue disease (MCTD). A major contribution of Sharp and his colleagues was to name and attempt to classify an overlap syndrome in explicit clinical terms and to associate it with specific autoantibodies directed against "extractable nuclear antigen" (ENA). One year later, the first child with MCTD was reported, and in 1977 a series of 14 children with MCTD was first investigated.
Where does mixed connective tissue disease, in both children and adults, stand now after more than a decade of study? Directly, the concept of MCTD has focused our attention upon the description of overlapping features of the rheumatic diseases, and it has forced us to confront whether "lumping" or "splitting" descriptors serves the patient from a therapeutic or prognostic point of view.
Patterns of antihistone antibody specificity in systemic rheumatic disease. I. Systemic lupus erythematosus, mixed connective tissue disease, primary sicca syndrome, and rheumatoid arthritis with vasculitis
