[When is it a diagnosis of overlap syndrome?].

The connective tissue diseases comprise a group of syndromes of unknown etiology affecting as many as 1 person in 40, often with a predilection for the female sex. Included are: systemic lupus erytematosus (SLE), polymyositis and dermatomyositis, Sjögren syndrome, scleroderma and the vasculitis (polyarteritis nodosa, Wegener's, giant cell arteritis). There are patients who are not easily defined; having features overlapping with those of other connective tissue diseases. A variety of terms such as mixed connective tissue disease, undifferentiated connective tissue syndrome and overlap syndrome have emerged to describe such patients. Although many of these overlap syndromes are unlikely to have life-threatening consequences, they may be extremely debilitating and distressing, significantly reducing quality of life for the patient and his or her family. We present the case of a patient initially diagnosed with dermatomyositis and who eventually evolved to overlap syndrome by developing SLE.