Table 5.11 ). Two ANAs are strongly associated with systemic sclerosis. One directed against DNA topoisomerase I (anti-Scl 70) is highly specific and is associated with a greater likelihood of pulmonary fibrosis and peripheral vascular disease. The other, an anticentromere antibody, is associated with a higher likelihood of CREST syndrome. Patients with this syndrome have relatively limited skin disease, often confined to fingers, forearms and face, and subcutaneous calcifications. Involvement of the viscera, including esophageal lesions, pulmonary hypertension, and biliary cirrhosis, may not occur at all or occur late. In general, these patients live longer than those with systemic sclerosis with diffuse visceral involvement from the outset.
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Systemicsclerosis(commonlycalledscleroderma)ischaracterizedbyprogressivefibrosisinvolvingtheskin,gastrointestinaltract,andothertissues.
FibrosismaybetheresultofactivationoffibroblastsbycytokinesproducedbyTcells,butwhattriggersTcellresponsesisunknown.
Endothelialinjuryandmicrovasculardiseasearecommonlypresentinthelesionsofsystemicsclerosis,perhapscausingchronicischemia,butthepathogenesisofvascularinjuryisnotknown.
Inflammatory myopathies comprise an uncommon, heterogeneous group of disorders characterized by injury and inflammation of mainly the skeletal muscles that are probably immunologically mediated. Based on clinical, morphologic, and immunologic features, three disorders— polymyositis, dermatomyositis, and inclusion body myositis—have been described. Each may occur alone or with other immune-mediated diseases, particularly systemic sclerosis. These diseases are described in Chapter 22.
Mixed connective tissue disease is a disorder with clinical features that overlap those of SLE, systemic sclerosis, and polymyositis. The disease is characterized serologically by high titers of antibodies to U1 ribonucleoprotein. Typically, it presents with synovitis of the fingers, Raynaud phenomenon, and mild myositis. Renal involvement is modest, and there is a favorable response to corticosteroids, at least in the short term. Because these clinical features are shared with other diseases, mixed connective tissue disease may not be a distinct entity, and in fact it may evolve over time into classic SLE or systemic sclerosis. However, progression to other autoimmune disorders is not universal, and there may be a form of mixed connective tissue disease that is distinct from other autoimmune diseases. Serious complications of mixed connective tissue disease include pulmonary hypertension, interstitial lung disease, and renal disease.
Polyarteritis nodosa belongs to a group of disorders characterized by necrotizing inflammation of the walls of blood vessels that show strong evidence of an immunologic basis. Any type of vessel may be involved—arteries, arterioles, veins, or capillaries. These vasculitides are discussed in Chapter 10.
IgG4-related disease (IgG4-RD) is a newly recognized constellation of fibro-inflammatory disorders characterized by tissue infiltrates rich in IgG4 antibody-producing plasma cells and lymphocytes, particularly T cells, associated with fibrosis and obliterative phlebitis (