Doctor OhioHealth Grant Medical Center, Ohio, United States
Introduction: Hemolytic uremic syndrome (HUS) is a potentially life-threatening condition characterized by the triad of microangiopathic hemolytic anemia (MAHA), thrombocytopenia, and acute kidney injury (AKI). It is one of many thrombotic microangiopathies (TMA). HUS is classified into typical and atypical variants. The most common cause of typical HUS is infection with Shiga toxin producing Escherichia coli (STEC). The atypical process has been linked to certain infections, medications, and immune processes. Legionella pneumophila, the causative agent of Legionnaires’ disease is primarily associated with pneumonia but there have been rare case reports of legionella as a cause of atypical HUS.
Description: 62-year-old male presented to the hospital with the chief complaints of weakness, poor oral intake, decreased and dark urine, and shortness of breath for 10 days. Physical exam showed hypoxia that corrected with 3L NC, tachypnea and left sided lower lobe crackles. He was transferred to the ICU for worsening hypoxia and required intubation. Admission labs were significant for thrombocytopenia, hyponatremia, azotemia and AKI. Urine antigen and BAL were positive for Legionella and he was treated with azithromycin and Levaquin. Throughout admission, platelet and hemoglobin levels continued to decrease. Elevated LDH, undetectable haptoglobin, and negative direct antibody suggested MAHA. Two sessions of plasmapheresis were done which led to improvement in azotemia, thrombocytopenia, and mentation. Plasmapheresis was discontinued with clinical improvement and once TTP was ruled out.
Discussion: Legionella infection is a rare cause of atypical HUS. This case highlights the importance of considering HUS in the differential in patients presenting with the HUS triad in the setting of Legionella infection. The pathophysiology of TMA involves the formation of platelet microthrombi in the endothelium which causes platelet consumption leading to thrombocytopenia and nonimmune mediated hemolytic anemia. This patient’s ADAMS TS13 was mildly decreased at 34%. Levels between 30-67% can be seen in patients who have TMA from non-idiopathic TTP conditions such as HUS, ITP or HIT. HUS, although rare, can be associated with Legionella infection.
