A 60‐year‐old woman presented with acute shortness of breath at rest requiring intubation. She denied any preceding fever, chills, chest pain, or diarrhea. Her medical history included stage IV gallbladder cancer treated with 6 cycles of gemcitabine. The last dose of chemotherapy was completed 1 month prior to presentation. She was afebrile and normotensive on presentation. She was found to be cachectic on exam. Mental status was normal. Diffuse crackles were auscultated. Abdominal exam showed no tenderness. Initial laboratory evaluation revealed hemoglobin of 8.3 g/dL and creatinine of 2.3 mg/dL Platelet count on presentation was 256/μL that dropped to 30/μL over the next 4 days. C3 level was 50 mg/dL, and C4 level was 20 mg/dL Peripheral smear revealed schistocytes. Because of concern for thrombotic thrombocytopenic purpura (TTP), 7 days of plasmapheresis was performed. She failed to improve with plasmapheresis. On day 7 of treatment, ADAMTS13 level returned at 60%, and complement factor I returned within low normal range as 32.7. Complement factor H level was still pending. With a normal ADAMTS13 level, the patient was diagnosed with atypical hemolytic uremic syndrome.
It is critical for the hospitalist to understand the workup and differential diagnosis of hemolytic anemia. Recognition of atypical hemolytic uremic syndrome (HUS) as a potential etiology is a key. Although many of these patients are triaged with concern for TTP, many of these patients can have other dangerous forms of anemia. Atypical HUS is a life‐threatening disease that, if recognized early, is potentially curable. Atypical HUS is a rare disorder in adults and clinically presents with a hemolytic anemia, schistocytosis, thrombocytopenia, and renal impairment. Although typical HUS presents with a preceding infection with Shiga‐like toxin or Streptococcus pneumoniae and often accompanied by bloody diarrhea, atypical HUS has no such preceding infection. Atypical HUS arises as either a familial form or as a sporadic form that is often preceded by a history of HIV, cancer, pregnancy, or the use of certain anticancer drugs including gemcitabine. It is caused by an overactivation of the alternate complement pathway that leads to uninhibited initiation of the membrane attack complex and subsequent cell injury and thrombosis. In our case, either the gallbladder cancer or the gemcitabine treatment acted as a nidus for uninhibited complement activation.
Although the extensive gallbladder disease precluded further treatment, atypical HUS can effectively be treated with the use of plasmapheresis or the novel complement factor 5a inhibitor eculizumab. The disease's rapid progression and effective treatment emphasize the importance of the hospitalist recognizing, diagnosing, and managing atypical hemolytic uremic syndrome.
To cite this abstract:Mohiuddin A. Atypical Hemolytic Uremic Syndrome. Abstract published at Hospital Medicine 2013, May 16-19, National Harbor, Md. Abstract 238. https://www.shmabstracts.com/abstract/atypical-hemolytic-uremic-syndrome/. Accessed February 18, 2019.