paroxysmal cold hemoglobinuria (PCH), a rare autoimmune hemolytic anemia disorder marked by hemolysis minutes or hours after exposure to cold. Characterized by the presence of a biphasic hemolysin, called the Donath-Landsteiner antibody, which hemolyzes red cells after exposure to cool temperatures and then warming back to 37° C. Systemic symptoms include the passage of dark urine, severe pain in the back and legs, headache, vomiting, diarrhea, and moderate reticulocytosis. Temporary hepatosplenomegaly and mild hyperbilirubinemia may follow the onset of an attack.
