Nineteen-month-old girl with persistent fever.

CASE REPORT: A 19-month-old girl with right fourth-degree vesicoureteral reflux and left small non-functional kidney was admitted with a 6-day 39°C fever. She was receiving antibiotic prophylaxis (amoxicillin-clavulanate) for urinary tract infections (UTIs). At admission, she had been taking ciprofloxacin for 2 days due to leucocyturia and nitrites shown by the urine dipstick without urine culture test being done. She appeared pale and in pain, although the clinical examination was unremarkable. Refill time was of 2-3 s. Urine and blood cultures (while assuming ciprofloxacin) were sterile. Procalcitonin and C reactive protein were 5.7 ng/mL and 10.55 mg/dL, respectively. Ceftazidime was started. After 2 days, we observed splenomegaly, haemoglobin level reduction from 95 g/L to 72 g/L, platelet level reduction from 195 000 to 89 000/µL, alanine aminotransferase (ALT) 466 U/L, aspartate aminotransferase (AST) 572 U/L, ferritin 553 ng/mL, triglycerides 434 mg/dL and d-dimer 2377 µg/L. Due to the persistence of fever after 48 hours of ceftazidime, it was replaced by meropenem because of suspected lobar nephritis sustained by multiresistant bacteria. QUESTION 1: Which of the following is the most likely diagnosis?Monocytic leukaemia.Hemophagocytic lymphohistiocytosis (HLH).Renal abscess/acute lobar nephritis.Macrophage activation syndrome (MAS). QUESTION 2: How would you manage this condition?Monitoring while continuing meropenem administration.Abdomen CT.Corticosteroid administration.Bone marrow aspirate. QUESTION 3: How would you confirm your diagnostic suspicions?Genetic testing.Immunological profile (soluble interleukin [IL-2] receptor alpha, tests of natural killer (NK) cell function, expression of perforin and granzyme).Neither A nor B.Both A and B. Answers can be found on page 2.