The autoimmune disorders are a protean group of acquired diseases in which genetic factors also play a role. They have in common widespread immunologic alterations and often share features of generalized inflammation.
Because of overlapping clinical features, differentiation among autoimmune diseases may be challenging, particularly in their early stages. These illnesses share certain clinical features, and differentiation among them is often difficult because of this. Common findings include synovitis, pleuritis, myocarditis, endocarditis, pericarditis, peritonitis, vasculitis, myositis, skin rash, and nephritis. Laboratory tests may reveal Coombs-positive hemolytic anemia, thrombocytopenia, leukopenia, immunoglobulin excesses or deficiencies, antinuclear antibodies, rheumatoid factors, cryoglobulins, false-positive serologic tests for syphilis, other antiphospholipid antibodies, elevated muscle enzymes, and hypocomplementemia.
Some of the laboratory abnormalities found in autoimmune diseases (eg, false-positive serologic tests for syphilis, rheumatoid factor) occur in asymptomatic individuals. These changes may also be demonstrated in certain asymptomatic relatives of patients with connective tissue diseases, in older persons, in patients using certain medications, and in patients with chronic infectious diseases.