Influenza A(H1N1) Infection Complicated by Hemolytic Uremic Syndrome in an Older Adult: A Case Report

Influenza A(H1N1) is a rare trigger for thrombotic microangiopathy (TMA), most often presenting as hemolytic uremic syndrome (HUS).HUS is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury.Some cases of influenza-associated HUS are thought to result from direct viral injury to the vascular endothelium, while others may reflect influenza triggering complement activation in individuals with an underlying complement regulatory defect.We report a case of an 80-year-old woman admitted with influenza A(H1N1) pneumonia who developed HUS.Thrombotic thrombocytopenic purpura was considered unlikely, as the activity of ADAMTS13 was not severely reduced.She recovered without dialysis or disease-specific treatment such as plasma therapy or complement inhibition.This case highlights the diagnostic challenges of TMA in the setting of influenza infection and the importance of early expert input in management.It also illustrates that recovery from influenzaassociated HUS with best supportive care is possible, although an underlying complement predisposition cannot be excluded without further testing.