A boy with fever, cough and gross haematuria

A 5 year-old boy presented with 2-days of fever and cough. On examination, he had mild dyspnoea and chest pain, with crackles and hypoventilation at the right lung base. Blood tests showed: WBC 39.1×109/L; N 28.9×109/L; Hb 11.3gr/dL; PLT 375×109/L; CRP 28.7mg/dL; ESR 41mm/h. Chest x-ray confirmed a pulmonary consolidation in the right lower lobe (figure 1), with an associated pleural effusion. Bacterial pneumonia was diagnosed and intravenous ceftriaxone 100mg/kg/die was started. The following day, he developed palpebral oedema and his urine became tea coloured. His blood pressure was 126/82mmHg (>99th percentile).1 Serum creatinine rose from 0.45mg/dl to 1.09mg/dl (39.8µmol/L - 93.4µmol/L) and C3 was 9mg/dl (n.r. 90-180mg/dl). Urinalysis revealed gross hematuria and 3+ proteinuria, with microscopicy showing dysmorphic red blood cells with casts. Ultrasounds showed enlarged kidneys with increased echogenicity.