Her blood tests revealed CRP of 23 mg/L, haemoglobin (Hb) of 90 g/L, white cell count (WCC) of 6.0 x 109/L, lymphocyte count of 0.57 x 109/L (Table 1), normal liver, and renal function tests, as well as complement C4 of 0.47 g/L and complement C3 of 1.29 g/L. The procalcitonin (PCT) came normal (0.07 ug/L), with a urine protein creatinine ratio (PCR) of 29.5 mg/mmol. Blood and urine cultures were negative. Viral PCR was negative for any infection. The gene discussed is C3; the disease is infection.