Background Hemolytic-uremic syndrome (HUS) is the most common cause of acute kidney injury in children. It is characterised by microangiopathic (nonimmune, Coombs-negative) hemolytic anaemia, thrombocytopenia and progressive acute renal failure. The classic form (typical HUS) is associated with a Shiga-like toxin often related to E. coli serotype O157:H7. The atypical HUS (aHUS) form is due to an overactivation of the alternative pathway of complement and carries a reserved prognosis with high mortality and morbidity in the acute phase. Eculizumab is effective in blocking the complement activation, being considered a first-line treatment in aSHU.

Case Herein, we present the case of a 21 month UK girl on holidays in Portugal who presented with a 6 day persistent diarrhoea (with no blood or mucus), fever and progressive prostration in the previous 24 hours. Upon observation, she revealed dehydration signs and blood tests showed a normal haemoglobin (11,5 g/dL), a low platelet count (86000/uL) and an increased urea (64 mg/dL) and creatinine (1,15 mg/dL). She was started on IV fluids. A 12 hours reevaluation revealed limb and orbital oedema and anaemia (Hg 8,7 g/dL), worsening thrombocytopenia (54000/uL) and renal impairment (creatinine 2,05). In the first 4 days she developed oliguria, general oedema, urea retention (242 mg/dL) and a creatinine of 5,19 mg/dL and was started on a peritoneal dialysis (PD). Complement preliminary studies showed a low C3 and C4. Due to the rapid renal deterioration a decision was made to start Eculizumab (rapid test to E. coli O157:H7 was negative) and prophylactic ceftriaxone. She was then repatriated to the UK on day 6. There, she continued intermittent PD over the next 2 weeks and gradually improved her condition. Renal function was normal, at our understanding, on discharge. Later stool bacteriological studies identified an E. coli (not O157:H7), but no further investigation was possible.

Discussion/conclusion Typical and atypical SHU may often share symptoms and clinical findings. The need of a prompt intervention in the acute phase can directly influence the prognosis, specially in aSHU, in which the decision to start Eculizumab is advised to taken on an early stage. Our case refers to a difficult intervention choice based on little laboratory information available at the time which led to a presumptive aSHU diagnosis even thought, retrospectively, the late findings were consistent with a more typical presentation.