Extraarticular manifestations of rheumatoid arthritis and HLA antigens in northern Italy.

We performed retrospective analysis of 141 Northern Italian patients with rheumatoid arthritis (RA). This series represents all the patients seen as in and/or outpatients at the rheumatologic unit of Reggio Emilia Hospital during a 2 year period (1987-88). We observed a low frequency of nodules (16%) and vasculitis (2.1%). Thus, RA seems to be milder in our population compared to Caucasian patients with RA originating from North America or England. We observed a weak association with DR4 (RR = 2.4) in the total group of patients with RA. A low frequency of DR4 was observed in patients and controls (29 vs 14.5%, p = 0.001). When compared with controls the frequency of DR4 was significantly higher in seropositive (p = 0.001), but not in seronegative patients. We found that DR4 was significantly associated with nodules (RR = 6.4), with extraarticular features (EAF) (RR = 4) and with erosions (RR = 3) compared with controls. The subgroups with nodules and EAF had a DR4 frequency (respectively, of 52 and 40%) which was significantly higher than that observed in remaining patients (respectively, 25 and 24%). No significant difference was observed in the DR4 frequency between the patients with erosions and those without (34 vs 18%). Thus, DR4 in our population seems to be predominantly associated with a subgroup of patients characterized by seropositivity and EAF.