Anti-proteinase 3 antibodies in diffuse systemic sclerosis (SSc) with normotensive renal impairment: is it suggestive for an overlapping between SSc and idiopathic vasculitis?

OBJECTIVE: To test the prevalence of anti-neutrophil cytoplasmic antibodies (ANCA) in systemic sclerosis (SSc) and to verify a possible association of ANCA with normotensive renal involvement in SSc. PATIENTS AND METHODS: 51 patients affected by SSc, 35 with diffuse scleroderma (dSSc) and 16 with limited scleroderma (lSSc), were tested for ANCA by indirect immunofluorescence (IIF) on human ethanol and formalin-acetone-fixed granulocytes (before and after DNase treatment), by conventional enzyme linked immuno-sorbent assay (ELISA) and by capture-ELISA. RESULTS: Six out of 51 selected SSc patients had ANCA by IIF (11.7%) and five presented a perinuclear/nuclear atypical ANCA pattern. In all cases we only found anti-proteinase3 (aPR3) antibodies. All ANCA positive patients had diffuse form of SSc (17.1%), all were anti-Scl70 positive (aScl70), five patients had proteinuria, three had microscopic haematuria. All ANCA positive patients were normotensive with normal renin plasma levels, the mean erythrocyte sedimentation rate (ESR) was higher in this group compared to the other SSc patients. CONCLUSIONS: Our study shows that aPR3 is not rare in dSSc. According to the clinical and serological findings and to the recent literature, we can hypothesise that when ANCA are found in SSc, an overlapping of scleroderma with systemic necrotizing vasculitis should be suspected.