Onset age is a risk factor for refractory pediatric IgA vasculitis: a retrospective cohort study.

BACKGROUND: Though outcome differences between children and adults with immunoglobulin A vasculitis (IgAV) has been well documented, it remains unclear if disease features in pediatric IgAV patients vary with onset age. We aimed to explore clinical features and prognosis of pediatric IgAV stratified by onset age. METHODS: We retrospectively reviewed records of patients under 18 years old diagnosed with IgAV from January 1999 to December 2018 in one tertiary medical center in Taiwan. Patients were grouped by onset age: ≤ 6 years old, 6-12 years old (> 6, ≤ 12), and 12-18 years old (> 12, < 18). Demographics, laboratory data, incidence of gastrointestinal, renal, and joint involvement, corticosteroid dependence, recurrence, and refractory disease were analyzed. Recurrence was defined as disease flare-up after complete remission and discontinuation of all medications for at least 3 months. Corticosteroid dependence was defined by more than 6 weeks of daily oral corticosteroid intake. Refractory disease was defined as not achieving complete remission 6 months after disease onset. Statistical analysis was performed using R software (v3.6.0). RESULTS: There were 484 IgAV patients, with an onset age of 6.10 (4.72-8.58) (median (IQR)) years old. There were 234 (48.3%) patients ≤6 years old, 210 (43.4%) 6-12 years old, and 40 (8.3%) 12-18 years old. One hundred and thirty (26.9%) patients had renal involvement, which was more frequent in older children (≤ 6 years old, 18.4%; 6-12 years old, 31.0%; 12-18 years old, 55.0%; p <  0.001). There were 361 patients (74.6%) with joint involvement; younger children were affected more frequently (≤ 6 years old, 82.1%; 6-12 years old, 71.9%; 12-18 years old, 45.0%; p <  0.001). Gastrointestinal involvement was present in 311 (64.3%) patients, showing no difference among age groups. There were 46 patients (9.5%) with recurrent IgA vasculitis, 136 (28.1%) with corticosteroid dependent and 76 (15.7%) with refractory disease. Corticosteroid dependence and refractory disease occurred more frequently as onset age increased (p <  0.001). CONCLUSION: Pediatric IgAV with different onset ages are associated with distinct clinical manifestations and outcomes. The risk of developing corticosteroid dependence, refractory disease and renal involvement increased with onset age.