Abstract Introduction Catastrophic thrombotic microangiopathy (TMA) includes a group of rare, life-threatening diseases that cause widespread microvascular thrombosis, multiorgan ischemia, and organ failure. Atypical hemolytic uremic syndrome (aHUS) is a complement-mediated disorder that commonly manifests with microvascular renal injury, thrombocytopenia, and hemolysis. Additionally, aHUS may present with atypical characteristics, including arterial thromboses and initially normal platelet counts, complicating diagnosis and treatment. It is imperative to rapidly identify complement-mediated TMA as targeted therapies, such as Eculizumab, improve patient outcomes. Case Presentation 69-year-old female with no PMH presented with a sudden onset of bilateral lower extremity weakness, numbness, and difficulty ambulating. Physical examination revealed distal sensory loss below the knees, 2/5 motor strength, cool pale feet, absent femoral to distal pulses with femoral Doppler signal only. CTA revealed acute thrombosis of the bilateral renal and splenic arteries with corresponding infarcts (Figure 1). The patient underwent urgent bilateral femoral cutdowns, multi-vessel thrombectomies and fasciotomies. Later developed cardiogenic shock, acute renal failure requiring SLED, and experienced pulseless electrical activity arrest with ROSC. Laboratory studies revealed precipitous thrombocytopenia, severe anemia, marked hemolysis with LDH 5000 U/L, hypocomplementemia, and undetectable haptoglobin. ADAMTS13 level was 56% excluding TTP. Autoimmune and hypercoagulability screens were negative. Despite plasma exchange, pulse steroids and heparin the patient succumbed to multiorgan failure. Discussion This case illustrates the intricacies of aHUS, a complement-mediated TMA. The patient had a rare catastrophic phenotype characterized by arterial thromboses in major arteries and multi-organ involvement, hence broadening the disease spectrum. The cause of aHUS is dysregulation of the alternative complement system, leading to endothelial damage and microvascular thrombosis. This makes it hard to diagnose because it often happens with other thrombotic microangiopathies, such as thrombotic thrombocytopenic purpura (TTP). Hypocomplementemia and the lack of ADAMTS13 deficiency are significant diagnostic markers. In the past plasma exchange was the mainstay of treatment but outcomes were poor with high rates of progression to end-stage renal disease and mortality. Eculizumab has improved outcomes for most patients by inducing hematologic remission. Early identification and management are crucial particularly for atypical presentations. This case exemplifies the importance of clinical suspicion, laboratory assessment, and multidisciplinary management of rapidly progressive TMA. Conclusion Atypical hemolytic uremic syndrome can present as a rapidly progressive TMA with extensive multi-organ arterial thromboses and severe complement consumption. This atypical presentation highlights the need for heightened clinical suspicion, comprehensive laboratory evaluation, and early initiation of complement inhibition to improve outcomes in catastrophic TMA. This abstract is funded by: None
Ramjas et al. (Fri,) studied this question.