Once bitten, twice shy

Abstract

A 48yr old man presented with a 1-2 week history of diarrhoea and fever. He took occasional ibuprofen for migraines but took no regular medications and was fit and active. On presentation to A+E blood tests revealed severe AKI with hyperkalaemia, low platelets and anaemia with raised inflammatory markers. He complained of shortness of breath with a CXR consistent with ARDS. He was commenced on IV antibiotics and was transferred to ITU for further management. While on ITU his blood film revealed evidence of haemolysis, in addition to an LDH of >2600. He had persistenly low platelets (14 at its nadir), requiring platelet transfusion. His renal failure was managed with haemofiltration and he was transfused to maintain his Hb above 80. The diagnosis was of haemolytic uraemic syndrome due to a presumed infectious origin. Blood cultures came back positive for a fastidious, slow-growing Gram-negative rod, identified as Capnocytophaga canimorsus. Further questioning revealed the presence of a dog bite to his R. index finger two months previously. The patient's antibiotic regimen was changed to Ceftriaxone 2g IV OD and metronidazole 500mg IV TDS and he was transferred to the Royal Free Hospital to commence haemodilaysis and for specialist renal management. Capnocytophaga canimorsus is an encapsulated organism known for its potential to cause disseminated and fatal infection in asplenic or immunocompromised patients, which were risk factors not present in our case. It is a rare cause of HUS and highlights the need for thorough history if an infective agent is presumed.