[A morphologic contribution to the pathogenesis of psoriatic arthritis (author's transl)].

Examination by light- and transmission electron microscopy of synovial tissues from 11 patients with psoriatic arthritis revealed several morphologic pictures. Besides the previously well described zones of fibrosis and degeneration of superficial cells, now the following were shown: 1. vascular alterations, especially of endotheliocytes, 2. transitional forms among endotheliocytes, perivascular cells, and fibroblasts as well as 3. lymphoidfollice-like accumulations of round cells. These changes could indicate the presence of an exogenous agent with perhaps strong antigenic effect but in low concentration. Such findings could be interpreted as indicating that in psoriasis there is an immunologic process in stratum synoviale which leads through abnormal cell proliferation and fibrosis to the final destructive event, osterarthritis and ankylosis.