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A3412 - Everything’s Atypical About this Atypical Hemolytic Uremic Syndrome
Author Block: F. Yousufi, S. N. Mahmood; MedStar Washington Hospital Center, Washington, DC, United States.
Introduction
Hemolytic uremic syndrome (HUS) is a triad of microangiopathic hemolytic anemia, acute kidney injury (AKI) and thrombocytopenia which is typically caused by shiga-toxin related to E. Coli infection. Complement mediated HUS is an atypical (diarrhea-negative) form of HUS and here we describe an atypical case of atypical HUS complicated by heart failure.
Case
36 year old female presented 6 months postpartum with nausea and vomiting. Labs were significant for an AKI with nephrotic range proteinuria, thrombocytopenia, elevated LDH and low haptoglobin with peripheral smear showing schistocytes suggesting microangiopathic hemolysis. Direct antiglobulin test was negative and complement levels found to be low and patient was diagnosed with postpartum atypical HUS. Course was subsequently complicated by admission to cardiac ICU due to volume overload secondary to new onset systolic heart failure with ejection fraction of 30% on echocardiography. Cardiac catheterization did not show coronary disease and renal biopsy showed MPGN like proliferative glomerular changes consistent with aHUS. Patient was started on eculizumab with improvement in her thrombocytopenia, anemia along with kidney function and systolic function.
Discussion
Complement mediated hemolytic uremic syndrome is an uncommon cause of thrombotic microangiopathy. Diagnosis is one of exclusion and involves ruling out other causes of HUS including Shiga-toxin producing E. Coli, pneumococcal, vitamin B12 disorders, as well as evaluation of ADAMTS13 activity for evaluation of TTP. When presenting in the postpartum period, it most commonly occurs weeks after delivery but cases up to 4 months have been reported, whereas our patient developed aHUS 6 months postpartum.
Complement mediated HUS causes increased activation of complement on endothelial cells causing microvascular thrombi and subsequent hemolytic anemia and kidney injury. Cardiac involvement can develop in up to approximately 10% of patients with aHUS. Though the mechanism is unclear it is thought to be related to ischemia secondary to microvascular thrombi. Anti-complement therapy is the primary treatment for complement mediated HUS which is important in preventing progression to ESRD. Given the intended decrease in complement activity, meningococcal vaccination is recommended. Our patient is unique in that she presented with aHUS and cardiomyopathy out of the usual time period for these diseases. This case highlights the importance of diagnosis of atypical HUS to allow prompt initiation of eculizumab to prevent mortality and minimize permanent organ damage. Finally this case highlights the development of cardiomyopathy as an important, but uncommon complication of atypical HUS.