U1 and systemic sclerosis: In sera from 203 Japanese patients with SSc, ACA was present in 77 (38%), anti-topo I in 67 (33%), anti-RNAP in 12 (6%), anti-U1 RNP in 11 (5%), anti-Th/To in seven (3%), anti-U3 RNP in five (2%), and no presence of ANA in 10 patients (5%).