[Pathophysiology and laboratory diagnosis of collagen diseases (author's transl)].

Beginning with lesions of the capillary wall, rheumatoid arthritis is morphologically expressed by an aseptic inflammation of the synovia with following necrosis of the cartilage and the underlying bone tissue. Only little is known regarding the pathogenesis but most porbably immune mechansims are involved. There is evidence for the participation of type IV and type III-reactions i.e. sensitized lymphocytes as well as immune complexes. Equally the etiology of RA is totally unknown. Once the inflammatory process has reached some activity, in most cases it shows the character of a selfpertetuation as in other autoimmune diseases. Laboratory examinations include BSR, blood count, measurement of Fe, Cu, RF, complement, streptolysins, staphylolysins, ANA, and in doubtful cases synovial biopsy. Furthermore, effusion fluid of the joint may be examined for RF, ANA, complement, rhagocytes, crystals, protein content etc.--Among the collagen diseases sensu strictori, systemic lupus erythematosus is the most important. The underlying process may be characterized as vasculitis due to immune complexes and local activation of the complement system, the complexes containing native and/or denatured DNA, and antibodies mostly of the IgG class. Laboratory examinations include the demonstration of ANA but should concentrate on the measurement of DNA-antibodies using radioimmunological or at least a sensitive and specific immunofluorescence technique. The value of the various tests is discussed.