Exploring the Intersection of Atypical Hemolytic Uremic Syndrome and Substance Use: A Comprehensive Narrative Review.

Hemolytic uremic syndrome (HUS) is a thrombotic microangiopathy characterized by hemolytic anemia, renal failure, and thrombocytopenia. While the typical form of HUS is often associated with Shiga toxin-producing (STEC) infections, atypical hemolytic uremic syndrome (aHUS) is caused by uncontrolled complement system activation, leading to endothelial damage, microthrombi formation, and other complications. Although aHUS is commonly linked to genetic mutations and infections, emerging evidence suggests that certain substances, particularly illicit drugs like heroin, cocaine, and ecstasy, can also trigger this condition, adding complexity to its diagnosis and management. This narrative review examines the mechanisms by which substance use can lead to aHUS, discusses its clinical presentation, and highlights the diagnostic challenges in distinguishing it from other thrombotic microangiopathies, such as thrombotic thrombocytopenic purpura (TTP) and STEC-HUS. A thorough literature search identified relevant case reports, case series, and observational studies, underscoring the need for genetic testing and complement assays to confirm aHUS in substance users. The review also explores the role of complement inhibitors, such as eculizumab and ravulizumab, which target the underlying pathophysiology and have shown promise in improving patient outcomes. However, the management of substance-induced aHUS remains challenging due to limited data, varying clinical presentations, and the need to optimize treatment protocols. Early recognition and tailored therapy are crucial for effective management. Further research is needed to refine diagnostic criteria, develop new therapeutic approaches, and improve care for patients with this under-recognized condition.