An anti‐i biphasic hemolysin in chronic paroxysmal cold hemoglobinuria

Abstract
Paroxysmal cold hemoglobinuria (PCH) was diagnosed in an elderly patient with a history of chronic lymphocytic leukemia. In this case, the Donath‐Landsteiner antibody demonstrated anti‐i specificity rather than the more commonly reported anti‐P specificity. This unusual case of a biphasic hemolysin with anti‐i specificity emphasizes the importance of performing a Donath‐Landsteiner test when presented with serological or clinical findings that are suggestive of PCH.