Introduction: Hemolytic uremic syndrome (HUS) is clinically diagnosed from the triad of microangiopathic hemolytic anemia, thrombocytopenia, and renal injury. So-called ”typical” (Shiga toxin or ST-HUS) is most often caused by Shiga toxin producing E. coli O157:H7 infection1. Alternatively, “atypical” or complement-mediated HUS (CM-HUS) has a genetic component and is caused by uncontrolled complement activation triggered by a variety of etiologies2. Clostridioides difficile (C.diff) is a Gram-positive spore forming bacteria that is transmissible through a fecal-oral route that present with colitis. HUS as a complication of CDI is rare, with only 11 cases reported in adults.
Case Description/Methods: A 43-year-old female with a past medical history of hepatic encephalopathy, peptic ulcer disease was found unconscious with a 3-day history of diarrhea, diaphoresis, and chills. Initial blood pressure was 186/97 mmHg and pulse of 110. Lactate dehydrogenase was 1223 U/L, creatinine 6.5 mg/dL, haptoglobin < 10 mg/dL, platelets 98 K/uL, and had schistocytes on peripheral blood smear. Concern was for thrombotic thrombocytopenia purpura (TTP). However, after patient’s ADAMTS13 protease level came back normal and inhibitor level undetectable, the leading diagnosis became HUS. Renal biopsy showed thrombotic microangiopathy without fibrosis. Stool pathogen panel was only positive for C.diff. After complement and genetic susceptibility panel labs returned negative for complement-mediated HUS, the leading diagnosis was typical HUS. The patient was started on oral vancomycin, plasmapheresis and hemodialysis with dramatic improvement after only a few sessions of plasmapheresis and doses of vancomycin. Eventually hemodialysis was stopped.
Discussion: Our patient presented with the classic triad of HUS with a renal biopsy showing thrombotic microangiopathy, confirming the diagnosis of HUS (Figure 1). The patient was found to have a negative Shiga toxin assay which would suggest an atypical cause of HUS, especially in an adult population. However, the patient had normal advanced complement studies and genetic studies which ruled out CM-HUS. This makes our patient’s presentation unique as she presented with typical HUS as an adult that was caused by an organism not commonly associated with HUS. In addition, our case was the only one to confirm the diagnosis of HUS by renal biopsy with further classification of “typical” HUS with negative advanced complement and genetic studies.
