The clinical relevance of serum antinuclear antibodies in Japanese patients with systemic sclerosis

BACKGROUND Systemic sclerosis (SSc) is a connective tissue disorder with excessive fibrosis of the skin and various internal organs. Although SSc is a heterogeneous disease, it has been reported that the particular antinuclear antibodies (ANA) are often indicative of clinical features, disease course and overall severity. OBJECTIVE To clarify the association of clinical and prognostic features with serum ANA in Japanese patients with SSc. METHODS We studied 203 Japanese patients diagnosed with SSc, who visited our hospital during the period 1983-2005. Six SSc-related ANA were identified using indirect immunofluorescence, double immunodiffusion and immunoprecipitation assays. RESULTS Patients with SSc were classified into six ANA-based subgroups and a group without ANA. As expected, antitopoisomerase I antibody (Ab, n=64), anti-RNA polymerases (RNAP) Ab (n=12) and anti-U3 RNP Ab (n=5) were associated with diffuse cutaneous SSc, whereas anticentromere Ab (ACA, n=75), anti-Th/To Ab (n=7) and anti-U1 RNP Ab (n=10) were frequently detected in patients with limited cutaneous SSc. Clinical features of the ANA-negative group (n=10) were heterogeneous. Consistent with previous findings in Caucasian and/or black African patients, antitopoisomerase I Ab was associated with the involvement of vascular and pulmonary fibrosis, leading to decreased survival rate. However, no patients with anti-RNAP Ab developed renal crisis and the frequency of isolated pulmonary hypertension in patients with ACA, anti-Th/To Ab or anti-U3 RNP Ab was similar to that in other ANA-based subgroups. CONCLUSION These results indicate that the clinical relevance of SSc-related ANA in Japanese patients differs in some aspects from that in Caucasian and/or black African patients.