Serum complement is a measure of disease activity in SLE as it indicates activation and consumption of complement components,21 Median complement levels differed significantly between age groups, with higher complement levels in younger patients [C3: 0.95 g/L (0.73–1.11) in pre-pubertal patients vs. 0.81 g/L (0.50–1.22) in peri-pubertal vs. 0.69 g/L (0.28–0.98) in adolescent patients (p = 0.002); C4: 0.13 g/L (0.08–0.28) in pre-pubertal patients vs. 0.11 g/L (0.06–0.19) peri-pubertal patients vs. 0.08 g/L (0.04–0.14) in adolescent patients (p = 0.002)] (Table 3). The gene discussed is C4A; the disease is systemic lupus erythematosus.