Rheumatoid arthritis (R.A.) factor in near relatives of sero-positive and sero-negative patients with rheumatoid arthritis.

In a previous publication (de Blcourt, Polman, and de Blcourt-Meindersma, 1961), we drew attention to the familial occurrence of rheumatoid arthritis and ankylosing spondylitis, each of which shows a special hereditary factor, but we did not report on the presence or absence of the so-called rheumatic factor in probands and members of the family. The "epidemiology" of various rheumatic conditions, including rheumatoid arthritis, has been the subject of several international conferences,* and it has been stated by various workers (for instance, Lawrence and Ball, 1958; Bremner, Alexander, and Duthie, 1959; Ziff, Schmid, Lewis, and Tanner, 1958; Ziff, 1961; Karten, DiTata, McEwan, and Tanner, 1962) that more persons with rheumatoid arthritis and/or positive serological reactions (showing the presence of the so-called rheumatoid factor) are found among the near relatives of sero-positive rheumatoid arthritics than among those of sero-negative arthritics. In near relatives of sero-positive rheumatoid arthritics, Lawrence and Ball (1958) found 20 per cent. with a positive Waaler-Rose test (as modified by Ball, 1950), and in a "mixed" group of seropositive and sero-negative probands they found 13 per cent. sero-positive relatives. In a group of normal controls, there were only 3 per cent. seropositive persons (so-called false positives). Ziff and others (1958) found 16 per cent. seropositive near relatives in a group of sero-positive rheumatoid arthritics, and 1 per cent. false positives in a control group. Bremner and others (1959) found no significant difference in results of the Waaler-Rose test in the