Diagnostic Overlap in HUS: an Atypical Case
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Publication Date
4-29-2026
Keywords
oregon, ppmc, ppmc gme
Disciplines
Medical Education
Abstract
Introduction: Atypical HUS (aHUS) is a rare type of Thrombotic Microangiopathy distinguished by complement dysregulation and overall clinical progression. We present a diagnostically ambiguous case with early intervention that preserved end-organ function with discussion of future pregnancy implications. Case Presentation: A 36yo F (G2P1) with hypothyroidism, Small Intestinal Bacterial Overgrowth (SIBO), and intermittent urticarial rashes presented with fever, abdominal pain, and 3 days of bloody diarrhea. Discussion: This case highlights an atypical presentation of aHUS with diarrheal prodrome and normal complement function, features that typically suggest Shiga toxin–mediated HUS. We saw clinical change after admission, allowing real-time monitoring. Maintaining a diagnostic framework increased confidence in aHUS diagnosis despite inconclusive data. 30-40% of aHUS cases can occur with normal complement (C3/C4) levels. Eculizumab, FDA approved for aHUS in 2011, is a humanized anti-C5 monoclonal Ab superior to plasma therapy for aHUS2 yet it remains cost prohibitively expensive. Early Eculizumab initiation (7 days post symptom onset) improves hematologic and renal outcomes. We had access to and started Eculizumab within 48 hours of symptom onset, This patient's quick recovery and avoidance of organ damage reinforces the importance of early aHUS treatment, even amidst diagnostic uncertainty
Specialty/Research Institute
Graduate Medical Education
Specialty/Research Institute
Internal Medicine
