An unusual trigger for a rare hemolytic anemia: paroxysmal cold hemoglobinuria after shingles and COVID-19

Abstract Paroxysmal cold hemoglobinuria (PCH) is a rare autoimmune hemolytic anemia that commonly presents as a transient, post-infectious disease mediated by biphasic Donath-Landsteiner antibodies, which bind to red blood cells at cold temperatures but cause hemolysis at core body temperature. PCH is less common in adults but can be a complication of infection or hematologic malignancy. One viral trigger of PCH that has rarely been described is that of primary varicella-zoster virus (VZV). Here, we report the case of a 69-year-old man who developed severe PCH following an episode of shingles, raising the possibility of a temporal relationship between PCH and VZV reactivation. Erythrophagocytosis and rosetting of red blood cells around neutrophils, smear findings commonly seen in PCH, were observed on the patient’s blood smear and aided in our diagnosis. Initial hemolysis testing demonstrated complement component 3-positive, immunoglobulin G-negative direct antiglobulin testing. Donath-Landsteiner testing confirmed a diagnosis of PCH. The patient had a complicated 38-day hospital course that required mechanical ventilation, renal replacement therapy, and extensive transfusions. Notably, the patient was also diagnosed with COVID-19 shortly before the onset of hemolysis, representing a potential alternative trigger or co-trigger to his PCH. Although the clinical timeline is compatible with VZV reactivation triggering PCH, the specific infectious trigger cannot be definitively established. Nevertheless, to our knowledge, this is the first reported case of PCH occurring in temporal association with VZV reactivation rather than primary VZV infection.