Case Presentation: A 29-year-old man with ulcerative colitis and autoimmune hepatitis (both diagnosed at age 15) was admitted to the hospital with a month-long history of hematochezia complicated by anemia and kidney injury. Historically, the patient’s AIH and UC was managed with an immunosuppressive medley; however, the patient had not used any medications within the past year. On presentation, the patient was afebrile, SBP in the 120s, and tachycardic to high 90s. Labs were significant for hemoglobin 2.4, and creatinine 3.1. He was admitted to the medicine ICU, where he began reporting coca-cola colored urine. A renal ultrasound showed intrinsic parenchymal injury, and UA showed large blood and low complement levels.On downgrade from the ICU, EGD and colonoscopy showed a Mayo 2 UC flare. He continued to have multiple bloody diarrhea each day, with continuous drops in hemoglobin levels. The precipitousness of the patient’s hemoglobin drop, despite multiple PRBC transfusions per day, was thought to be out of proportion to the degree of UC flare and amount of bloody diarrhea he exhibited. In addition, since admission, the patient’s platelets had also been dropping, with concomitant rises in BUN and creatinine, indicating a concurrent thrombotic microangiopathy pathology. These findings, along with decreased urine output, flank pain, and unresolved cola-colored urine despite aggressive fluid resuscitation, prompted immediate work-up for hemolytic anemia. ASO, ANA, anti-dsDNA, anti-GBM, SPEP/UPEP levels were all normal. C-ANCA was negative, P-ANCA and Protein-3 antibody were high. LDH was found to be markedly high, haptoglobin essentially undetectable, and blood smear showed fragmented RBCs. ADAMTS13 and G6PD activities were normal, Coombs test and Shiga stool toxin were negative. Complement protein C3 was low, C4 was normal. HIT screen was negative. The patient had also been on a moderate dosage of corticosteroids since admission for his active UC flare, which is the first line treatment for most TMAs, including HUS and TTP, thus making these diagnoses unlikely. With these findings, there was high suspicion for atypical HUS. The patient was immediately started eculizumab weekly infusions.Following his first dose of eculizumab, the patient improved significantly. Hgb and plt uptrended, BUN and creatinine downtrended, and his BM became formed and non-bloody. He was discharged with Uceris for his UC, continued weekly eculizumab, with outpatient hematology and GI clinic follow up. Complement studies were also sent for further diagnostic workup.

Discussion: The development of atypical HUS in the course of active UC is a complication that has been reported six times at the writing of this abstract. Although the link between aHUS and UC still remains to be investigated, the improvement of GI and hematologic pathologies after eculizumab, a C5 inhibitor, in our patient, as well as the six previously reported cases, indicates a role of the alternative complement pathway in the development of both these diseases. Interestingly, two recently reported cases involved the development of aHUS in the context of poorly managed IBD, similar to our patient, suggesting a possible risk factor for developing aHUS in this patient population.

Conclusions: Although infrequent, the association between IBD and aHUS has been increasingly recognized and documented, and as such should be on the radar of any clinician managing a patient with an active IBD flare complicated by renal failure, thrombocytopenia, and transfusion-resistant anemia.