Delayed-Onset Hemolysis in a Case of Hemolytic Uremic Syndrome: A Diagnostic Challenge

Hemolytic uremic syndrome is a rare thrombotic microangiopathy characterized by hemolytic anemia, thrombocytopenia, and acute kidney injury. While commonly reported in children, adult-onset presentations are less frequent and often atypical, leading to diagnostic delays. This case underscores the importance of repeated evaluation when classical features are absent initially.

A 50-year-old woman was admitted with diarrhea, vomiting, abdominal pain, and visible hematuria. Initial findings included severe thrombocytopenia and Stage 3 acute kidney injury but no evidence of hemolysis. Blood cultures grew Escherichia coli sensitive to piperacillin-tazobactam. Despite intensive care management for septic shock, renal function deteriorated and renal replacement therapy was required. On Day 9 of admission, delayed hemolysis became evident with schistocytes on blood smear, undetectable haptoglobin, and hemoglobin decline from 125 g/L at baseline to 87 g/L. These findings confirmed delayed-onset hemolytic uremic syndrome. ADAMTS13 activity was not tested because TTP was considered clinically unlikely based on stable coagulation parameters and absence of neurological features. Supportive care, including renal replacement therapy and blood products, was provided, and the patient's renal function normalized before discharge.

This case highlights the diagnostic complexity of adult-onset hemolytic uremic syndrome, particularly when hemolysis develops late. Clinicians should maintain a high index of suspicion in adults presenting with unexplained acute kidney injury and thrombocytopenia, even in the absence of early hemolytic markers. Serial blood film reviews and multidisciplinary input are essential to avoid missed or delayed diagnosis. Early recognition enables timely supportive care and consideration of targeted therapies to prevent irreversible renal damage and long-term complications.