Familial occurrence of psoriatic arthritis.

Although the association between psoriasis and arthritis has been known since the original description by Alibert (1818), it is only recently that the condition has become widely acknowledged as a disease sui generis (Vilanova and Pifiol, 1951; Coste, Franqon, Touraine, and Loyau, 1958; Wright, 1959). The general acceptance of the disorder stems largely from epidemiological (Baker, 1965), clinical (Wright, 1956, 1961; Baker, Golding, and Thompson, 1963a), and radiological (Avila, Pugh, Slocumb, and Winkelmann, 1960) data reported over the last decade. Despite this advance in our knowledge of psoriatic arthritis, the cause of the disorder remains unknown, but several recent studies have suggested that genetic factors may be important in aetiology (Tiedemann, 1951; Baker, Golding, and Thompson, 1963b; Theiss, B6ni, Wagenhauser, Schnyder, and Fehr, 1969a; Theiss, Schnyder, Boni, and Wagenhauser, 1969b; Theiss, Schnyder, and Boni, 1970). In order to examine further the importance of heredity in this disease, a large controlled family survey of probands with psoriatic arthritis has been undertaken at Leeds over a 2-year period. It is the purpose of this paper to report the major findings of this study. Clinical material