Case Presentation:
A 72‐year‐old woman with no medical history presented with four days of epigastric pain and bloody diarrhea after eating an undercooked hamburger. Vital signs and basic labs were normal. Her abdomen was tender to palpation without rebound or guarding. Abdominal CT revealed diffuse colitis, so ceftriaxone and metronidazole were started. On day three, the patient developed hemolytic anemia with decreasing hemoglobin (11.3 to 9.4 g/dl), increasing bilirubin (total 1.0 to 4.0 mg/dl, direct 0.4 to 1.4 mg/dl), low haptoglobin (<7 mg/dl), and elevated LDH (1107 U/L). Decreasing platelets (176 x 10^3/ul to 70 x 10^3ul) and rising creatinine (0.78 to 1.50 mg/dl) were also observed. Peripheral blood smear revealed numerous schistocytes. Stool studies were negative for shiga toxin, E. coli 0157:H7, salmonella, campylobacter, and yersinia. Plasmapheresis and steroids were initiated with poor response. Hemodialysis was started on day eight for progressively worsening renal function. ADAMTS13 was negative, so eculizumab was started with rapid improvement in platelet count and renal function.
Discussion:
Hospitalists commonly encounter hemolytic anemia, and thrombotic microangiopathy should be considered in the differential. Hemolytic uremic syndrome (HUS) is typically a childhood disease and often overlooked in adults. HUS and thrombotic thrombocytopenic purpura (TTP) both present with hemolytic anemia, acute renal dysfunction, and thrombocytopenia, but HUS often presents with more severe renal dysfunction while TTP with more prominent neurological symptoms. The ADAMSTS13 should be obtained to differentiate between HUS and TTP.
HUS is categorized as typical or atypical. Typical HUS is mainly caused by shiga toxin‐producing E. coli (STEC), while atypical HUS is caused by dysregulation of the complement cascade, which can be inherited, acquired, or both. Atypical HUS has a poor prognosis; in one case series 46% of adults experiencing their first episode progressed to end‐stage renal disease. Stool studies help differentiate between atypical and typical HUS. Treatment of HUS is supportive with red blood cell and platelet transfusions, although platelet transfusions often worsen thrombocytopenia so should be used judiciously. Hemodialysis is often used temporarily until renal function improves. Plasmapheresis and steroids can be used but there is little evidence for their effectiveness. Eculizumab, a terminal complement inhibitor, has been shown to significantly improve renal function in atypical HUS.
Conclusions:
HUS should be considered in adult patients presenting with hemolytic anemia, acute renal dysfunction and thrombocytopenia. Hospitalists should consider using Eculizumab to treat atypical HUS if there is poor response to supportive therapy and typical treatments.