Ulcerative Colitis Gone Rogue: A Case of Complement-Mediated Thrombotic Microangiopathy in Inflammatory Bowel Disease

We present an unusual case of complement-mediated thrombotic microangiopathy (formerly known as atypical hemolytic uremic syndrome) associated with inflammatory disease in a young patient. A 26-year-old male patient with no significant past medical history presented to our emergency department with a four-week history of diffuse, moderate, cramping, non-radiating abdominal pain with no known aggravating or relieving factors. Abdominal pain was associated with nausea, vomiting, and bloody stools. His physical examination revealed pale conjunctiva, tachycardia, and mild tenderness in the lower abdomen. The patient's laboratory results indicated severe anemia with a hemoglobin level of 2.9 g/dL, an elevated white blood cell count of 52.86 K/uL, a low platelet count of 107 K/uL, and evidence of acute kidney injury, with a blood urea nitrogen level of 87.0 mg/dL and a serum creatinine level of 8.32 mg/dL. Further work-up showed hemolysis, characterized by low haptoglobin levels, elevated lactate dehydrogenase, and a positive direct Coombs test for both anti-IgG and anti-C3 antibodies. A computed tomography angiogram (CTA) of the abdomen and pelvis showed pancolitis. Severe inflammation was noted during a flexible sigmoidoscopy, and pathology results revealed chronic inflammation/chronic colitis. A renal biopsy performed showed thrombotic microangiopathic changes with complement deposition. The patient was started on eculizumab, which ultimately resulted in improvements in anemia, thrombocytopenia, and renal function. Our case stands out as the complexity of the diagnosis warrants awareness of complement-mediated thrombotic microangiopathy (TMA). The introduction of eculizumab, a terminal complement blockade therapy, has revolutionized the management of complement-mediated TMA, as early initiation of eculizumab treatment has shown significant reductions in disease progression to end-stage kidney disease and its related complications.