Introduction to Connective Tissue Disorders and Autoimmune Conditions

A variety of pathologic processes affect the connective tissues. The chapters that follow this one address some of these conditions with special emphasis on autoimmune disorders (e.g. rheumatoid arthritis, scleroderma, systemic lupus erythematosus, dermatomyositis/polymyositis, Sjögren syndrome, mixed connective tissue disease, and vasculitis), amyloidosis and eosinophilic lung disease. An autoimmune response is an immune response that targets an antigen within the host and attacks healthy body tissues. This often involves T and B lymphocytes in a response that is very similar to an allergic reaction. While the presence of an auto-antibody is often an essential component of the autoimmune response, its mere presence does not define the disease. In addition to the presence of auto-antibodies, the presence of soft tissue damage is required, thus auto-antibodies may be present in the absence of an inflammatory process. Amyloidosis is a pathologic entity with protean manifestations, often thought of as a single disease rather a group of diseases that share a similar pathophysiologic event: the deposition of proteins within the soft tissues. The term eosinophilic lung disease encompasses a wide variety of pathologic conditions that range from idiopathic diseases to systemic vasculitides and, in some cases, a response to parasitic infestation.