All patients included in this study met 4 or more classification criteria for SLE as proposed by the American College of Rheumatology 1997 revised criteria.29,30 We consider juvenile SLE patients those who began their disease before age 16. We included 30 patients with juvenile SLE and 92 adult SLE patients in the study, from 7 reference centers in Argentina: Center for Medical Education and Clinical Research Norberto Quirno (CEMIC), Italian Hospital of Buenos Aires, Acute General Hospital José Penna, Hospital de Clinicas José de San Martín, Acute General Hospital Juan Antonio Fernández, Hospital San Martín de La Plata, Buenos Aires British Hospital and Pediatrics Hospital Prof. Dr. Juan P. Garrahan.

A specific questionnaire was designed for the study, where clinical data based on the examination and review of the clinical history of the patient was collected. Clinical manifestations presented by patients from diagnosis to the time of inclusion in the study (cumulative events) were detailed. The following events were considered: Discoid rash, oral ulcers, photosensitivity, alopecia, malar rash, Raynaud's phenomenon, leukopenia, hemolytic anemia, thrombocytopenia, serositis, arthritis, psychosis, seizures, neuropathy, transverse myelitis, acute confusional state, glomerulonephritis, vasculitis, dry mouth, dry eyes. Information was obtained on treatments received from the time of diagnosis of the disease to inclusion in the study. Activity was calculated using the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) at the time of sample collection. Antibody results were also recorded during the patient's history (ANA, anti-DNA, anti-Ro/SSA, anti-La/SSB, anti-Sm, and anti-nRNP).

All participants signed informed consent; the study was conducted after approval by the ethics committees of each institution.

Blood samples for determination of antibodies were taken in the participating centers, and were analyzed centrally in the CEMIC laboratory of Immunology and Rheumatology. Measurement of anti-Ro/SSA, anti-La/SSB, anti-Sm, and anti-nRNP antibodies was performed by double-diffusion technique. The anti-P ribosomal antibodies were evaluated by enzyme-linked immunosorbent assay (ELISA) using as antigen, a purified protein from bovine and/or rabbit thymus (ImmunoVision, Inc.) absorbed at 0.5μg/well (Maxisorb polystyrene plate; Nunc). Samples were considered positive when values ≥11U. Measurement of anti-Ro/SSA, anti-La/SSB, anti-Sm, and anti-P ribosomal antibodies nRNP was performed simultaneously on all samples.

Qualitative variables are presented as numbers and percentages, and quantitative variables as mean/median and standard deviation/minimum and maximum values. To determine an association, we employed chi-square (χ2) or Fisher exact tests. To quantify the strength of association we used odds ratios (OR) and their 95% confidence intervals (95% CI). For analysis of the SLEDAI in patients with positive and negative anti-P ribosomal antibodies and between adult vs juveniles, Wilcoxon and Mann–Whitney's tests were used. Significance was considered as a P<.05. Statistical analysis was performed using the Epi Info statistical package™ 7 (Centers for Disease Control and Prevention [CDC]).

Twenty-four patients (80%) in the youth group and 81 (88%) adults had Caucasian ethnicity. Two (6.7%) of the patients with juvenile SLE and 6 (6.5%) patients in the adult SLE group were males. The mean age at diagnosis in patients with juvenile SLE was 12.67±3.56 and for adults, 30±11.46 years. The mean age of patients at the time of inclusion in the study was 22.9±8.4 and 39.76±12.37 years for the group of juvenile and adult SLE respectively; the average duration of the disease at the time of inclusion in the study was 10.63±7.16 years in youths and 9.36±7.75 years in adults.

Clinical manifestations and treatment received:

The prevalence of different clinical manifestations in both groups (adults and juveniles) is detailed in Table 1. Malar rash (OR=3.9, 95% CI=1.1–14.25), photosensitivity (OR=2.64, 95% CI=1.03–6.76), vasculitis (OR=5.33, 95% CI=1.7–16.0), non-discoid rash (OR=3.0, 95% CI=1.09–8.4) and neurological involvement: seizures (OR=3.85, 95% CI=1.12–13.22) and psychosis (OR=4, 95% CI=1.15–13.79) were found more frequently in the juvenile SLE. Five adult patients developed neurological manifestations (not in the ACR criteria): cognitive impairment in 3 patients, peripheral sensory polyneuropathy of the lower limbs in 1 patient and 1 patient with acute confusional state. No patient developed transverse myelitis or multiple mononeuritis.

Patients used the following immunosuppressive therapy: methotrexate (MTX), mycophenolate mofetil (MMF), azathioprine (AZA), cyclophosphamide (CF), glucocorticoids (prednisone or equivalent) >20mg; there were no statistically significant differences between adult and juvenile patients or between the patients positive or negative anti-P ribosomal antibodies (data not shown). Adult patients received hydroxychloroquine more frequently than juveniles (95.6% vs 83.3%; P=.025).

The SLEDAI score in the total population (adults and juveniles) was mean 3.89 (SD 4.68) in patients with juvenile SLE and 5.11 (SD 5.33) and 3.56 in adults (SD 4.44; P=.09).

The prevalence of antibodies is detailed in Table 2. Of the antibodies determined, the presence of anti-P ribosomal antibodies (OR=5.21, 95% CI=1.6–16.5) was significantly higher in the group of patients with juvenile SLE.

Table 3 shows the prevalence of other autoantibodies in patients with adult and juvenile SLE, according to whether they were positive or negative for anti-P ribosomal antibodies. The prevalence of all other autoantibodies was similar in both groups.

Table 4 shows the prevalence of anti-P ribosomal antibodies detailed according to the clinical manifestations. Alopecia (OR=10.11, 95% CI=1.25–97) and skin rash (non-discoid) (OR=4.1, 95% CI=1.25–13.89) were the only clinical manifestations that were significantly associated with the presence of anti-P ribosomal antibodies.

The SLEDAI score in the population with negative anti-P ribosomal antibodies was, on average 3.93 (SD 4.76) and, in patients with positive anti-P ribosomal antibodies, on average 3.58 (SD 4.12; P=.97).

The authors declare that this research has not performed experiments on humans or animals.

The authors declare that they have followed the protocols of their workplace on the publication of data from patients and all patients included in the study have received sufficient information and gave written informed consent to participate in the study.

The authors have obtained informed consent from patients and/or subjects referred to in the article. This document is in the possession of the corresponding author.