Clinical usefulness of anti-neutrophil cytoplasmic antibodies in childhood systemic lupus erythematosus

Not so many studies evaluating the prevalence and the clinical usefulness of ANCA in childhood systemic lupus erythematosus (SLE) have been published. Furthermore, the interference of antinuclear antibodies (ANA) with ANCA detection has been described. This study was designed to detect ANCA prevalence in children with SLE, avoiding ANA interference. In order to differentiate certain groups displaying vasculitis or glomerulonefritis, the antigenic specificity of ANCA and their association with the disease activity. Different clinical features were also assessed. A total of 51 patients (mean age, 14.6 years) were studied. SLE was established following the American College of Rheumatology criteria. Patients were clustered according to the Disease Activity Index (SLE-DAI). ANCA were detected by indirect immunofluorescence (IFI). Antigenic specificity was characterized by a lineal qualitative home-made immunoassay (LIA-Blot). Interference by ANA and native anti-DNA antibodies (aDNAn) was avoided by specific sorbents. Prevalence of pANCA and aANCA was 9.8% (5/51) and 5.9% (3/51), respectively. Anti-myeloperoxidase (aMPO) and anti-lactoferrin (aLf) frequencies were 9.8% (5/51) and 13.7% (7/51), respectively. No cANCA, anti-proteinase 3 or anti-elastase antibodies were detected. Both pANCA and aMPO, alone or associated, proved to be related to the presence of glomerulonephritis (p=0.02, chi square), but not to the SLE-DAI. This study asserts the presence of ANCA in children with SLE. In addition, a significant association of pANCA and anti-MPO with glomerulonephritis was found. Further studies including larger number of patients are needed to assess the association of ANCA with other clinical features.