Acute Progression of Adult-Onset Atypical Hemolytic-Uremic Syndrome due to CFH Mutation: A Case Report

Atypical hemolytic-uremic syndrome (aHUS), unlike typical HUS, is not due to bacteria but rather to an idiopathic or genetic cause that promotes dysregulation of the alternative complement pathway. It leads to hemolytic anemia, thrombocytopenia, and renal impairment. Although aHUS secondary to a genetic mutation is relatively rare, when occurring due to a mutation in Factor H (CFH), it usually presents with younger onset and has a more severe course, which in the majority ends with end-stage renal failure. Paradoxically to most available data, our case features acute aHUS due to a CFH mutation with late onset (38-year-old) and rapid progression to end-stage renal disease. Due to current data indicating a high risk of graft failure in such patients, the diagnosis of aHUS secondary to a genetic cause has disqualified our patient from a living (family) donor renal transplantation and left her with no other option but to begin permanent renal replacement therapy. 1. Introduction Hemolytic-uremic syndrome (HUS) is characterized by hemolytic anemia, thrombocytopenia, and renal failure. It is most frequently caused by Shiga-like toxin bacterial infections in the digestive tract, such as from Escherichia coli [1]. Atypical HUS (aHUS) refers to non-Shiga-toxin HUS, a primary disease due to a disorder of alternative complement pathway regulation; it represents only 5–10% of HUS in children, but the majority in adults [2]. aHUS is a rare renal disease, about two per one million in the United States, with 80% of cases due to a sporadic and 20% a familial form [2, 3]. Diagnosis of aHUS requires the exclusion of other associated diseases, a lack of criteria for typical HUS, and a lack of criteria for thrombotic thrombocytopenic purpura determined with serum ADAMTS 13 activity [2]. Historically, these patients tend to have a poorer prognosis than those with typical HUS, with an acute aHUS mortality of 8% [4], and with 50%–80% of patients progressing to end-stage renal failure. Individuals with aHUS frequently relapse even after complete recovery from the presenting episode; this course of illness is more likely to be genetic in origin [1]. In patients with aHUS, mutations were reported in the genes of three proteins that regulate the alternative complement pathway: Factor H (CFH), membrane cofactor protein (MCP or CD46), and Factor I (IF) [5–8]. Plasma infusion or exchange has been done to reduce mortality, and patient surveillance should be continued on a regular basis to check for markers of renal failure and problems with RBC, hemoglobin (Hb), and platelet